Retarders and circular polarizers

ABSTRACT

A novel retarder comprising a long transparent substrate, and up on the substrate, a first and a second optically anisotropic layers formed from a homogenously aligned rod-like liquid crystal compound and having a phase shift substantially equal to π measured and equal to π/2 respectively at a wavelength of 550 nm; and a first alignment layer having a rubbing axis defining the azimuthal direction of the homogenous alignment in the first anisotropic layer. The angle between the slow axis of the first anisotropic layer and the longitudinal direction of the transparent substrate is 75°, the angle between the slow axis of the second anisotropic layer and the longitudinal direction is 15°, the angle between the slow axis of the second anisotropic layer and the slow axis of the first anisotropic layer is 60° and the azimuthal direction of the homogenous alignment in the first anisotropic layer is substantially orthogonal to the rubbing axis of the first alignment layer.

FIELD OF THE INVENTION

[0001] The present invention relates to retarders (preferably a phaseretardation film) that are useful as λ/4 plates in reflective liquidcrystal display devices, pickups for writing on optical discs oranti-reflection coatings; circular polarizers using said retarders; andpreparation processes thereof. Particularly, the present inventionrelates to retarders comprising a long transparent substrate andoptically anisotropic layers having a laminate structure of rod-likeliquid crystals formed thereon by coating; circular polarizers that canbe prepared by laminating such a retarder to a polarizer in aroll-to-roll manner; and preparation processes thereof.

DESCRIPTION OF RELATED ART

[0002] λ/4 plates find great many applications and have already beenpractically used. However, most of λ/4 plates achieve λ/4 only at aspecific wavelength though they are called λ/4 plates. JP-A 1998-68816and JP-A 1998-90521 (the term “JP-All as used herein means an“unexamined published Japanese patent application”) disclose retardersobtained by laminating two optically anisotropic polymer films. In theretarder described in JP-A 1998-68816, a quarter-wave plate forming abirefringence light with a phase difference of a quarter wavelength anda half-wave plate forming a birefringence light with a phase differenceof a half wavelength are laminated with their optic axes being crossed.In the retarder described in JP-A 1998-90521, at least two retardershaving a retardation value of 160-320 nm are laminated at an angle withtheir slow axes being neither parallel nor orthogonal to each other. Theretarders described in both documents specifically having laminatestructures of two polymer films. Both documents explain that λ/4 can beachieved in a wide wavelength region with this arrangement. However, thepreparation processes of the retarders described in JP-A 1998-68816 andJP-A 1998-90521 require cutting two polymer films at a predeterminedangle and laminating the resulting chips in order to control the opticaldirections (optic axes or slow axes) of the two polymer films. Ifretarders are to be prepared by laminating chips, the process becomescomplex and other disadvantages occur such as liability to qualityfailure due to misalignment, decrease in yield, increase in cost andliability to deterioration due to contamination. Moreover, it isdifficult to strictly control the retardation value in polymer films.

[0003] On the other hand, techniques for more easily providing abroadband λ/4 plate by including at least two optically anisotropiclayers containing a liquid crystal compound are disclosed in JP-A2001-4837, JP-A 2001-21720 and JP-A 2000-206331. Especially, thetechnique disclosed in JP-A 2001-4837, in which the same liquid crystalmolecules can be used, is also attractive in terms of production costs.

[0004] During the preparation of a retarder by laminating opticallyanisotropic layers containing a liquid crystal compound, it is importantto control the alignment of the liquid crystal compound. For example,optically anisotropic layers can be formed of homogenously alignedrod-like liquid crystal compounds with respect to a substrate. If alayer containing a rod-like liquid crystal compound is formed on analignment layer subjected to a rubbing treatment, the rod-like liquidcrystal compound is normally homogenously aligned with the long axisbeing in the rubbing direction. However, our careful studies revealedthat the accuracy of liquid crystal alignment decreased when aconventional alignment layer is used for an alignment of liquid crystalmolecules in a direction of the rubbing axis to form the liquid crystalmolecular layer disclosed in JP-A 2001-4837. It was also found that manyoptical defects occurred with some types of rod-like liquid crystalcompounds or with some types of liquid crystal compositions.

SUMMARY OF THE INVENTION

[0005] In view of the problems described above, the present inventionaims to provide a retarder (preferably a phase retardation film) thatcan perform in a broad wavelength range (visible wavelength range) andcan be easily and stably prepared in a thin-layer form. The presentinvention also aims to provide a circular polarizer that can perform ina broad wavelength range (visible wavelength range) and can be easilyand stably prepared in a thin-layer form. The present invention alsoaims to provide a process by which a retarder and a circular polarizerperforming well in a broad wavelength range (visible wavelength range)and capable of being in a thin-layer form can be prepared by stablycontrolling the alignment of the molecules of the liquid crystalcompound. The present invention also aims to provide a novel techniquefor controlling the alignment of rod-like liquid crystals.

[0006] As a result of careful studies about retarders having laminatestructures of λ/4 liquid crystal layers and λ/2 liquid crystal layers,we found that when an alignment layer which allows liquid crystalmolecules to be aligned along the rubbing axis is used, the alignment ofthe liquid crystal molecules induced by the alignment layer is notstabilized though the rod-like liquid crystal compound should behomogenously aligned at a large azimuthal angle with respect to thelongitudinal direction of the transparent substrate to form a λ/2 liquidcrystal layer. We also found that liquid crystal molecules are alignedin various directions near free surfaces to bring about optical defectsin the liquid crystal molecules though the rod-like liquid crystals inthe λ/2 liquid crystal layer and λ/4 liquid crystal layer should behomogenously aligned with high accuracy. Further profound studies basedon these findings led us to accomplish the present invention.

[0007] In one aspect, the present invention provides a retarder(preferably a phase retardation film) comprising:

[0008] a long transparent substrate, and up on the substrate,

[0009] a first optically anisotropic layer formed from a homogenouslyaligned rod-like liquid crystal compound and having a phase shiftsubstantially equal to π measured at a wavelength of 550 nm;

[0010] a second optically anisotropic layer formed form a homogenouslyaligned rod-like liquid crystal compound and having a phase shiftsubstantially equal to π/2 measured at a wavelength of 550 nm; and

[0011] a first alignment layer having a rubbing axis defining theazimuthal direction of the homogenous alignment of the rod-like liquidcrystal compound in the first optically anisotropic layer;

[0012] wherein the angle between the slow axis in the plane of the firstoptically anisotropic layer and the longitudinal direction of thetransparent substrate is substantially 75°, the angle between the slowaxis in the plane of the second optically anisotropic layer and thelongitudinal direction of the transparent substrate is substantially15°, the angle between the slow axis in the plane of the secondoptically anisotropic layer and the slow axis in the plane of the firstoptically anisotropic layer is substantially 60° and the azimuthaldirection of the homogenous alignment of the rod-like liquid crystalcompound in the first optically anisotropic layer is substantiallyorthogonal to the rubbing axis of the first alignment layer.

[0013] As preferred, there are provided the retarder comprising a secondalignment layer having a rubbing axis defining the azimuthal directionof the homogenous alignment of the rod-like liquid crystal compound inthe second optically anisotropic layer, wherein the angle between therubbing axis of the first alignment layer and the longitudinal directionof the transparent substrate is substantially −15° and the angle betweenthe rubbing axis of the second alignment layer and the longitudinaldirection of the transparent substrate is substantially 15°; theretarder wherein the first alignment layer is formed of at least onecopolymer having at least one of repeating units represented by any oneof formulae (I) to (III) below and at least one of repeating unitsrepresented by formula (IV) below:

[0014] wherein R¹ to R³ independently represent a hydrogen atom, ahalogen atom or an alkyl group having 1 to 6 carbon atoms; M representsa proton, an alkali metal ion or an ammonium ion; L⁰ and L¹independently represent a divalent linking group selected from the groupconsisting of —O—, —S—, —CO—, —NR⁴—, —SO₂—, alkylene groups, alkenylenegroups, arylene groups and combinations thereof; R⁴ represents ahydrogen atom or an alkyl group containing 1 to 6 carbon atoms; R⁰represents a C10-100 group containing at least two aromatic rings oraromatic heterocycles; Cy represents a condensed aromatic cyclichydrocarbon group or a condensed aromatic heterocyclic group; Qrepresents a polymerizable group; and m, n¹, n² and p represent the mol% of each repeating unit where m is 10-99 mol %, n¹ and n² are each 1-90mol % and p is 0.1-20 mol %; the retarder wherein the first opticallyanisotropic layer contains at least an agent for promoting homogenousalignment represented by formula (V) below:

(Hb-L²-)_(n)B¹  Formula (V)

[0015] wherein Hb represents an aliphatic group having 6 to 40 carbonatoms or an aliphatic-substituted oligosiloxanoxy group having 6 to 40carbon atoms; L² represents a divalent linking group selected from thegroup consisting of —O—, —S—, —CO—, —NR⁵—, —SO₂—, alkylene groups,alkenylene groups, arylene groups and combinations thereof; R⁵represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms;n represents an integer of any of 2 to 12; and B¹ represents an n-valentgroup containing at least three cyclic structures;

[0016] and wherein the tilt angle of the rod-like liquid crystalcompound is substantially less than 10°; and the retarder wherein therod-like liquid crystal compound in the first optically anisotropiclayer or the second optically anisotropic layer is at least one ofrod-like liquid crystal compounds of formula (VI) below:

Q¹¹-L¹¹-Cy¹¹-L¹²-(Cy¹²-L¹³)_(n)-Cy¹³L¹⁴-Q¹²  Formula (VI)

[0017] wherein Q¹¹ and Q¹² independently represent a polymerizablegroup; L¹¹ and L¹⁴ independently represent a divalent linking group; L¹²and L¹³ independently represent a single bond or a divalent linkinggroup; Cy¹¹, Cy¹² and Cy¹³ independently represent a divalent cyclicgroup; and n represents 0, 1 or 2.

[0018] In another aspect, the present invention provides a method forpreparing a retarder comprising the steps of:

[0019] forming a first alignment layer up on a long transparentsubstrate, said first alignment layer having a rubbing axis at an angleof substantially −15° with respect to the longitudinal direction of thetransparent substrate,

[0020] forming a first optically anisotropic layer by applying arod-like liquid crystal compound to the first alignment layer andhomogenously aligning the rod-like liquid crystal compound in anazimuthal direction substantially orthogonal to the rubbing axis of thefirst alignment layer, so as that the first optically anisotropic layerhas a phase shift substantially equal to π measured at a wavelength of550 nm,

[0021] forming a second alignment layer on the transparent substrate,said second alignment layer having a rubbing axis at an angle ofsubstantially 15° with respect to the longitudinal direction of thetransparent substrate, and

[0022] forming a second optically anisotropic layer by applying arod-like liquid crystal compound to the second alignment layer andhomogenously aligning the rod-like liquid crystal compound in anazimuthal direction substantially parallel to the rubbing axis of thesecond alignment layer, so as that the second optically anisotropiclayer has a phase shift substantially equal to π/2 measured at awavelength of 550 nm.

[0023] In another aspect, the present invention provides a circularpolarizer comprising:

[0024] a long transparent substrate having a front surface and rearsurface, and up on the front surface of the substrate,

[0025] a first optically anisotropic layer formed of a homogenouslyaligned rod-like liquid crystal compound and having a phase shiftsubstantially equal to π measured at a wavelength of 550 nm;

[0026] a second optically anisotropic layer formed of a homogenouslyaligned rod-like liquid crystal compound and having a phase shiftsubstantially equal to π/2 measured at a wavelength of 550 nm; and

[0027] a first alignment layer having a rubbing axis defining theazimuthal direction of the homogenous alignment of the rod-like liquidcrystal compound in the first optically anisotropic layer;

[0028] and on the rear surface of the substrate,

[0029] a polarizing film having a polarization axis substantiallyorthogonal to the longitudinal direction of the substrate;

[0030] wherein the angle between the slow axis in the plane of the firstoptically anisotropic layer and the longitudinal direction of thetransparent substrate is substantially 75°, the angle between the slowaxis in the plane of the second optically anisotropic layer and thelongitudinal direction of the transparent substrate is substantially15°, the angle between the slow axis in the plane of the secondoptically anisotropic layer and the slow axis in the plane of the firstoptically anisotropic layer is substantially 60° and the azimuthaldirection of the homogenous alignment of the rod-like liquid crystalcompound in the first optically anisotropic layer is substantiallyorthogonal to the rubbing axis of the first alignment layer.

[0031] In another aspect, the present invention provides a method forpreparing a circular polarizer comprising the steps of:

[0032] forming a first alignment layer up on a front surface of a longtransparent substrate, said first alignment layer having a rubbing axisat an angle of substantially −15° with respect to the longitudinaldirection of the transparent substrate,

[0033] forming a first optically anisotropic layer by applying arod-like liquid crystal compound to the first alignment layer andhomogenously aligning the rod-like liquid crystal compound in anazimuthal direction substantially orthogonal to the rubbing axis of thefirst alignment layer, so as that the first optically anisotropic layerhas a phase shift substantially equal to π measured at a wavelength of550 nm,

[0034] forming a second alignment layer on the transparent substrate,said second alignment layer having a rubbing axis at an angle ofsubstantially 15° with respect to the longitudinal direction of thetransparent substrate,

[0035] forming a second optically anisotropic layer by applying arod-like liquid crystal compound to the second alignment layer andhomogenously aligning the rod-like liquid crystal compound in anazimuthal direction substantially parallel to the rubbing axis of thesecond alignment layer, so as that the second optically anisotropiclayer has a phase shift substantially equal to π/2 measured at awavelength of 550 nm, and

[0036] forming a polarizing film on a rear surface of the substrate,having an absorption axis substantially parallel to the longitudinaldirection of the transparent substrate and a polarization axis in adirection substantially perpendicular to the longitudinal direction ofthe transparent substrate.

[0037] As used herein, the expressions “substantially 15°”,“substantially −15°”, “substantially 75°”, “substantially 60°”,“substantially parallel” and “substantially orthogonal” mean that eachangle is within the range of the exact angle ± less than 5°. The errorfrom the exact angle is preferably less than 4°, more preferably lessthan 3°. As used herein, the “slow axis” means the direction in whichthe refractive index is maximum and the “rubbing axis” means thedirection of rubbing. Also as used herein, the expressions “a frontsurface of a transparent substrate” and “a rear surface of a transparentsubstrate” simply mean the directions viewed from the transparentsubstrate, but should not be construed to limit embodiments in whichretarders and circular polarizers of the present invention are used.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038]FIG. 1 is a schematic diagram showing a basic structure of aretarder of the present invention.

[0039]FIG. 2 is a schematic diagram showing a typical structure of acircular polarizer of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] A retarder of the present invention comprises a transparentsubstrate, and a first optically anisotropic layer having a phase shiftsubstantially equal to π measured at a wavelength of 550 nm and a secondoptically anisotropic layer having a phase shift substantially equal toπ/2 measured at a wavelength of 550 nm, laminated at the top thereof.The first optically anisotropic layer contains a homogenously alignedrod-like liquid crystal compound, and the second optically anisotropiclayer contains a homogenously aligned rod-like liquid crystal compound.On the other hand, a circular polarizer of the present inventioncomprises a retarder of the present invention and a polarizing film atthe bottom of the transparent substrate of the retarder. In retardersand circular polarizers of the present invention, the order in which thefirst optically anisotropic layer and the second optically anisotropiclayer are laminated is not specifically limited, and either may becloser to the transparent substrate. In the present invention, theoptically anisotropic layers preferably consist of the first and secondoptically anisotropic layers.

[0041] Each of the first and second optically anisotropic layers mayachieve a phase shift of substantially equal to π or π/2 at a specificwavelength. However, they preferably achieve a phase shift of π or π/2at 550 nm, a wavelength near the center of the visible region. In orderto achieve a phase shift of π at a specific wavelength (λ), theretardation value of the optically anisotropic layer measured at thespecific wavelength (A) may be adjusted to λ/2. In order to achieve aphase shift of π/2 at a specific wavelength (λ), the retardation valueof the optically anisotropic layer measured at the specific wavelength(λ) may be adjusted to λ/4. That is, the first optically anisotropiclayer preferably has a retardation value of 240 to 290 nm, morepreferably 250 to 280 nm measured at a wavelength of 550 nm. The secondoptically anisotropic layer preferably has a retardation value of 0.110to 145 nm, more preferably 120 to 140 nm measured at a wavelength of 550nm.

[0042] The retardation value means the in-plane retardation value forthe light entered from the normal direction of the optically anisotropiclayer. Specifically, it is defined by the equation below:

Retardation value (Re)=(nx−ny)×d

[0043] where nx and ny mean the principal refractive indices in theplane of an optically anisotropic layer or a birefringent film, and d isthe thickness (nm) of the optically anisotropic layer or birefringentfilm. JP-A 1998-68816 contains an explanation of the achievement ofcircular polarization by the Poincare sphere.

[0044]FIG. 1 is a schematic diagram showing a basic structure of aretarder of the present invention. As shown in FIG. 1, a basic retarderhas a transparent substrate (S), a first optically anisotropic layer (A)and a second optically anisotropic layer (B). The first opticallyanisotropic layer (A) has a phase shift substantially equal to π, andthe second optically anisotropic layer (B) has a phase shiftsubstantially equal to π/2. The angle (α) between the longitudinaldirection (s) of the transparent substrate (S) and the slow axis (a) inthe plane of the first optically anisotropic layer (A) is 75°. Therubbing axis (ra) of the alignment layer and the slow axis (a) in thefirst optically anisotropic layer (A) are orthogonal to each other. Theangle (β) between the slow axis (b) in the plane of the second opticallyanisotropic layer (B) and the longitudinal direction (s) of thetransparent substrate (S) is 15°. The rubbing axis (rb) of the alignmentlayer and the slow axis (b) in the second optically anisotropic layer(B) have the same direction. And, the angle (γ) between the slow axis(b) in the plane of the second optically anisotropic layer (B) and theslow axis (a) in the plane of the first optically anisotropic layer (A)is 60°. The first optically anisotropic layer (A) and the secondoptically anisotropic layer (B) shown in FIG. 1 contain rod-like liquidcrystal molecules (c1 and c2). The rod-like liquid crystal molecules (c1and c2) are homogenously aligned. The longitudinal directions of therod-like liquid crystal molecules (c1 and c2) correspond to the slowaxes (a and b) in the planes of the optically anisotropic layers (A andB).

[0045]FIG. 2 is a schematic diagram showing a typical structure of acircular polarizer of the present invention. The circular polarizershown in FIG. 2 further comprises a polarizing film (P) in addition tothe transparent substrate (S), first optically anisotropic layer (A) andsecond optically anisotropic layer (B) shown in FIG. 1. In the samemanner as shown in FIG. 1, the angle (α) between the longitudinaldirection (s) of the transparent substrate (S) and the slow axis (a) inthe plane of the first optically anisotropic layer (A) is 75°, the angle(β) between the slow axis (b) in the plane of the second opticallyanisotropic layer (B) and the longitudinal direction (s) of thetransparent substrate (S) is 15°, and the angle (γ) between the slowaxis (b) in the plane of the second optically anisotropic layer (B) andthe slow axis (a) in the plane of the first optically anisotropic layer(A) is 60°. In addition, the polarization axis (p) of the polarizingfilm (P) and the longitudinal direction (s) of the transparent substrate(S) are orthogonal to each other. The first optically anisotropic layer(A) and the second optically anisotropic layer (B) shown in FIG. 2 alsocontain rod-like liquid crystal molecules (c1 and c2). The rod-likeliquid crystal molecules (c1 and c2) are homogenously aligned. Thelongitudinal directions of the rod-like liquid crystal molecules (c1 andc2) correspond to the slow axes (a and b) in the planes of the opticallyanisotropic layers (A and B).

[0046] Materials used for preparing retarders of the present inventionand preparation examples thereof are explained in detail below. Forconvenience of explanation, the following description relates toprocesses for preparing retarders in which the first opticallyanisotropic layer and the second optically anisotropic layer aresuccessively laminated on the transparent substrate, but the first andsecond optically anisotropic layers may be laminated in the reverseorder.

[0047] In a retarder of the present invention, a first alignment layerdefining the azimuthal angle of the homogenous alignment of the rod-likeliquid crystal compound contained in the first optically anisotropiclayer is first formed at on the transparent substrate.

[0048] The present invention is characterized in that an alignment layersubjected to a rubbing treatment is used to homogenously align therod-like liquid crystal compound in the first optically anisotropiclayer in a direction substantially orthogonal to the rubbing axis of thealignment layer so that the rod-like liquid crystal compound ishomogenously aligned in a direction at an angle of substantially 75°with respect to the longitudinal direction of the transparent substrate.When the optic axes of the molecules of the rod-like liquid crystalcompound are to be aligned at an angle greater than 45° with respect tothe longitudinal direction of the transparent substrate, stablealignment can be achieved by using an alignment layer that allows theoptic axes of the rod-like liquid crystal molecules to be aligned in adirection orthogonal to the rubbing direction (hereinafter referred toas an orthogonal alignment layer).

[0049] For example, a solution of a polymer constituting a material ofthe orthogonal alignment layer described below is applied on the surfaceof a long transparent substrate and dried to form a film, which is thensubjected to a rubbing treatment to form an orthogonal alignment layer.The rubbing process can be performed by rubbing the surface of the filmin a direction several times with paper or a cloth. In the presentinvention, the rubbing treatment can be performed in a direction at anangle of substantially −15° with respect to the longitudinal directionof the transparent substrate. That is, the rubbing process can beperformed in such a manner that the angle between the rubbing axis andthe longitudinal direction of the transparent substrate is substantially−15°. A coating solution containing a rod-like liquid crystal compoundis applied to thus formed orthogonal alignment layer, so that therod-like liquid crystal molecules are aligned in a direction at an angleof 90° with respect to the rubbing axis of the orthogonal alignmentlayer. That is, the rod-like liquid crystal compound can be aligned in adirection at an angle of 75” with respect to the longitudinal directionof the transparent substrate to form a first optically anisotropic layerhaving a phase shift of π.

[0050] The thickness of the orthogonal alignment layer is preferably0.01 to 5 μm, more preferably 0.05 to 1 μm.

[0051] The first alignment layer (orthogonal alignment layer) may beformed on a temporary substrate and the liquid crystal compound in thefirst optically anisotropic layer may be aligned and then the firstlayer may be transferred onto the transparent substrate. The liquidcrystal compound fixed in an alignment can remain the alignment withoutthe first alignment layer.

[0052] The first alignment layer is an orthogonal alignment layer whichallows the rod-like liquid crystal compound in the first opticallyanisotropic layer to be homogenously aligned in a directionsubstantially orthogonal to the rubbing axis. Materials that can beapplied to the present invention as materials for the orthogonalalignment layer are described in JP-A 2002-062427, JP-A 2002-098836,JP-A2001-254481 and Japanese Application No. 2000-174829. Especiallypreferred are orthogonal alignment layers formed of a copolymercomprising a repeating unit of any one of formulae (I), (II) and (III)below and a repeating unit of formula (IV) below:

[0053] wherein R¹ to R³ independently represent a hydrogen atom, ahalogen atom or an alkyl group having 1 to 6 carbon atoms; M representsa proton, an alkali metal ion or an ammonium ion; L⁰ and L¹independently represent a divalent linking group selected from the groupconsisting of —O—, —S—, —CO—, —NR⁴—, —SO₂—, alkylene groups, alkenylenegroups, arylene groups and combinations thereof; R⁴ represents ahydrogen atom or an alkyl group having 1 to 6 carbon atoms; R⁰represents a C10-100 group containing at least two aromatic rings oraromatic heterocycles; Cy represents a condensed aromatic cyclichydrocarbon group or a condensed aromatic heterocyclic group; Qrepresents a polymerizable group; and m, n¹, n² and p represent the mol% of each repeating unit where m is 10-99 mol %, n¹ and n² are each 1-90mol % and p is 0.1-20 mol %.

[0054] Formulae (I) to (III) above are explained in detail below.

[0055] In formula (I) above, R¹ represents a hydrogen atom, a halogenatom or an alkyl group containing 1 to 6 carbon atoms. R¹ preferablyrepresents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,more preferably a hydrogen atom, a methyl group or an ethyl group, mostpreferably a hydrogen atom or a methyl group. Compounds wherein R¹ is ahydrogen atom are acrylic copolymers and compounds wherein R¹ is methylare methacrylic copolymers.

[0056] In formula (I) above, M represents a proton, an alkali metal(e.g., Na, K) ion or an ammonium ion. The ammonium ion (includingprimary to quaternary ammonium ion) may be substituted by organic groups(e.g., methyl). Examples of ammonium ions include ⁺NH₄, ⁺NH₃CH₃, ⁺NH₂(CH₃)₂, ⁺NH(CH₃)₃ and ⁺N(CH₃)₄.

[0057] Acrylic copolymers of formula (I) above are soluble in waterbecause COOM is a hydrophilic group. Thus, the alignment layer can beformed with an aqueous solvent.

[0058] In formula (I) above, m represents the mol % of the repeatingunit in the range of 10 to 99 mol %. m is preferably 10 to 95 mol %,more preferably 25 to 90 mol %.

[0059] In formula (II) above, R² represents a hydrogen atom, a halogenatom or an alkyl group having 1 to 6 carbon atoms. R² preferablyrepresents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,more preferably a hydrogen atom, a methyl group or an ethyl group, mostpreferably a hydrogen atom or a methyl group.

[0060] In formula (II) above, L⁰ represents a divalent linking groupselected from the group consisting of —O—, —S—, —CO—, —NR⁴—, —SO₂—,alkylene groups, alkenylene groups, arylene groups and combinationsthereof, preferably —CO-L²- where —CO— is bonded to the backbone and-L²- represents a divalent linking group selected from the groupconsisting of —O—, —CO—, —NR⁴—, alkylene groups and combinationsthereof. L⁰ is preferably —CO—O—, —CO—NH—, —CO—O-alkylene-,—CO—O-alkylene-O— or —CO—O-alkylene-CO—O—, especially —CO—C— or —CO—NH—.The alkylene group may be branched or may have a cyclic structure. Thealkylene group preferably contains 1 to 30, more preferably 1 to 15,most preferably 1 to 12 carbon atoms.

[0061] In formula (II) above, R⁰ represents a substituted orunsubstituted C10-100 hydrocarbon group containing at least two aromaticrings or aromatic heterocycles, which may be substituted. The aromaticrings or aromatic heterocycles are preferably aromatic rings, preferablycontaining 6 to 18 carbon atoms. Examples of aromatic rings includebenzene, naphthalene, anthracene, phenanthrene, pyrene and naphthacenerings. Examples of aromatic heterocycles include pyridine and pyrimidinerings. Benzene and naphthalene rings are preferred, and benzene is mostpreferred.

[0062] Substituents that the aromatic rings or aromatic heterocycles mayhave include halogen atoms, carboxyl, cyano, nitro, carbamoyl,sulfamoyl, alkyl groups, cycloalkyl groups, alkoxy groups, alkylthiogroups, acyl groups, acyloxy groups, alkyl-substituted carbamoyl groups,alkyl-substituted sulfamoyl groups, amide groups, sulfonamide groups andalkylsulfonyl groups.

[0063] In formula (II) above, the group linking the plurality ofaromatic rings independently represents an ethynylene group, a singlebond, —CO—, —O—CO—, —CO—O—, -alkylene-O—, —CO—NH—, —O—CO—O—, —NHSO₂— or—NH—CO—O—. Preferably, at least one represents a single bond or anethynylene group.

[0064] In formula (II) above, n¹ represents the mol % of the repeatingunit in the range of 1 to 90 mol %. n¹ is preferably 5 to 80 mol %, morepreferably 10 to 70 mol %. Examples of repeating units having ahydrocarbon group having 2, 3 or 4 aromatic rings or aromaticheterocycles in the side chain are shown below.

[0065] Examples of acrylic copolymers containing a repeating unit havinga hydrocarbon group having 2, 3 or 4 aromatic rings or aromaticheterocycles in the side chain are shown below. AA means a repeatingunit derived from acrylic acid and MA means a repeating unit derivedfrom methacrylic acid. The proportion of each repeating unit isexpressed in mol %.

[0066] PA301: -(AA)₆₀-(VI-1)₄₀-

[0067] PA302: -(AA)₇₀-(VI-2)₃₀-

[0068] PA303: -(AA)₆₀-(VI-5)₄₀-

[0069] PA304: -(AA)₆₅-(VI-9)₅₅-

[0070] PA305: -(AA)₇₀-(VI-11)₃₀-

[0071] PA306: -(AA)₈₀-(VI-15)₂₀-

[0072] PA307: -(AA)₇₀-(VI-15)₃₀-

[0073] PA308: -(AA)₆₀-(VI- 15)₄₀-

[0074] PA309: -(AA)₇₀-(VI-16)₃₀-

[0075] PA310: -(AA)₆₀-(VI-16)₄₀-

[0076] PA311: -(AA)₅₀-(VI-16)₅₀-

[0077] PA312: -(AA)₇₀-(VI-18)₃₀-

[0078] PA313: -(AA)₆₀-(VI-18)₄₀-

[0079] PA314: -(AA)₅₀-(VI-18)₅₀-

[0080] PA315: -(AA)₆₀-(VI-23)₄₀-

[0081] PA316: -(AA)₆₀-(VI-25)₄₀-

[0082] PA317: -(AA)₆₀-(VI-32)₄₀-

[0083] PA318: -(AA)₆₀-(VI-35)₄₀-

[0084] PA319: -(AA)₆₀-(VI-37)₄₀-

[0085] PA320: -(AA)₆₀-(VI- 45)₄₀-

[0086] PA321: -(AA)₆₀-(VI-55)₄₀-

[0087] PA322: -(MA)₆₀-(VI-1)₄₀-

[0088] PA323: -(MA)₇₀-(VI-2)₃₀-

[0089] PA324: -(MA)₆₀-(VI-5)₄₀-

[0090] PA325: -(MA)₆₅-(VI-9)₃₅-

[0091] PA326: -(MA)₇₀-(VI-11)₃₀-

[0092] PA327: -(MA)₈₀-(VI-15)₂₀-

[0093] PA328: -(MA)₇₀-(VI-15)₃₀-

[0094] PA329: -(MA)₆₀-(VI-15)₄₀-

[0095] PA330: -(MA)₇₀-(VI-16)₃₀-

[0096] PA331: -(MA)₆₀-(VI-16)₄₀-

[0097] PA332: -(MA)₅₀-(VI-16)₅₀-

[0098] PA333: -(MA)₇₀-(VI-18)₃₀-

[0099] PA334: -(MA)₆₀-(VI-18)₄₀-

[0100] PA335: -(MA)₅₀-(VI-18)₅₀-

[0101] PA336: -(MA)₆₀-(VI-23)₄₀-

[0102] PA337: -(MA)₆₀-(VI-25)₄₀-

[0103] PA338: -(MA)₆₀-(VI-32)₄₀-

[0104] PA339: -(MA)₆₀-(VI-35)₄₀-

[0105] PA340: -(MA)₆₀-(VI-37)₄₀-

[0106] PA341: -(MA)₆₀-(VI-45)₄₀-

[0107] PA342: -(MA)₆₀-(VI-55)₄₀-

[0108] The repeating unit having a hydrocarbon group having 2, 3 or 4aromatic rings or aromatic heterocycles in the side chain preferably hasa tolan structure.

[0109] Examples of repeating units having a hydrocarbon group having 2,3 or 4 aromatic rings or aromatic heterocycles in the side chain havinga tolan (diphenylacetylene) structure are shown below.

[0110] Examples of acrylic copolymers containing a repeating unit havinga hydrocarbon group having 2, 3 or 4 aromatic rings or aromaticheterocycles in the side chain having a tolan structure are shown below.AA means a repeating unit derived from acrylic acid and MA means arepeating unit derived from methacrylic acid. EA and C1A mean repeatingunits of formulae below where M is as defined for M in formula (I) Theproportion of each repeating unit is expressed in mol %.

[0111] PA401: -(AA)₆₀-(VI-101)₄₀-

[0112] PA402: -(AA)₇₀-(VI-101)₃₀-

[0113] PA403: -(AA)₆₀-(VI-102)₄₀-

[0114] PA404: -(AA)₆₅-(VI-107)₃₅-

[0115] PA405: -(AA)₇₀-(VI-111)₃₀-

[0116] PA406: -(AA)₈₀-(VI-114)₂₀-

[0117] PA407: -(AA)₇₀-(VI-120)₃₀-

[0118] PA408: -(AA)₆₀-(VI-123)₄₀-

[0119] PA409: -(AA)₇₀-(VI-125)₃₀-

[0120] PA410: -(AA)₆₀-(VI-125)₄₀-

[0121] PA411: -(AA)₅₀-(VI-125)₅₀-

[0122] PA412: -(AA)₇₀-(VI-126)₃₀-

[0123] PA413: -(AA)₆₀-(VI-128)₄₀-

[0124] PA414: -(AA)₅₀-(VI-132)₅₀-

[0125] PA415: -(AA)₇₀-(VI-133)₃₀-

[0126] PA416: -(AA)₆₀-(VI-133)₄₀-

[0127] PA417: -(AA)₇₀-(VI-138)₃₀-

[0128] PA418: -(AA)₆₀-(VI-138)₄₀-

[0129] PA419: -(AA)₆₀-(VI-139)₄₀-

[0130] PA420: -(AA)₆₀-(VI-141)₄₀-

[0131] PA421: -(AA)₆₀-(VI-143)₄₀-

[0132] PA422: -(MA)₆₀-(VI-101)₄₀-

[0133] PA423: -(MA)₇₀-(VI-101)₃₀-

[0134] PA424: -(MA)₆₀-(VI-102)₄₀-

[0135] PA425: -(MA)₆₅-(VI-107)₃₅-

[0136] PA426: -(MA)₇₀-(VI-111)₃₀-

[0137] PA427: -(MA)₈₀-(VI-114)₂₀-

[0138] PA428: -(MA)₇₀-(VI-120)₃₀-

[0139] PA429: -(MA)₆₀-(VI-123)₄₀-

[0140] PA430: -(MA)₇₀-(VI-125)₃₀-

[0141] PA431: -(MA)₆₀-(VI-125)₄₀-

[0142] PA432: -(MA)₅₀-(VI-125)₅₀-

[0143] PA433: -(MA)₇₀-(VI-126)₃₀-

[0144] PA434: -(MA)₆₀-(VI-128)₄₀-

[0145] PA435: -(MA)₅₀-(VI-132)₅₀-

[0146] PA436: -(MA)₇₀-(VI-133)₃₀-

[0147] PA437: -(MA)₆₀-(VI-133)₄₀-

[0148] PA438: -(MA)₇₀-(VI-138)₃₀-

[0149] PA439: -(MA)₆₀-(VI-138)₄₀-

[0150] PA440: -(MA)₆₀-(VI-139)₄₀-

[0151] PA441: -(MA)₆₀-(VI-141)₄₀-

[0152] PA442: -(MA)₆₀-(VI-142)₄₀-

[0153] PA451: -(ClA)₆₀-(VI-145)₄₀-

[0154] PA452: -(EA)₆₀-(VI-146)₄₀-

[0155] PA453: -(ClA)₆₀-(VI-147)₄₀-

[0156] PA454: -(EA)₆₀-(VI-148)₄₀-

[0157] In formula (III) above, Cy represents an alicyclic group, anaromatic group or a heterocyclic group.

[0158] The aliphatic ring in the alicyclic group is preferably a5-membered to 7-membered ring, more preferably a 5-membered or6-membered ring, most preferably a 6-membered ring. Examples of thealiphatic ring include cyclohexane, cyclohexene and bicyclo [2.2.1]hepta-2-ene rings. The aliphatic ring may be condensed to anotheraliphatic ring, an aromatic ring or a heterocycle.

[0159] Examples of the aromatic ring in the aromatic group includebenzene, naphthalene, anthracene, phenanthrene, pyrene and naphthacenerings. The aromatic ring may be condensed to an aliphatic ring or aheterocycle.

[0160] The heterocycle in the heterocyclic group is preferably a5-membered to 7-membered ring, more preferably a 5-membered or6-membered ring. The heterocycle preferably has aromaticity. Thearomatic heterocycle is typically unsaturated and preferably has themaximum number of double bonds. Examples of the heterocycle includefuran, thiophene, pyrrole, oxazole, isoxazole, isothiazole, imidazole,pyrazole, furazane, pyran, pyridine, pyridazine, pyrimidine and pyrazinerings. The heterocycle may be condensed to another heterocycle, analiphatic ring or an aromatic ring.

[0161] The alicyclic, aromatic and heterocyclic groups may besubstituted. Examples of the substituents include alkyl groups (e.g.,methyl, ethyl, t-butyl), substituted alkyl groups (e.g., chloromethyl,hydroxymethyl, chlorotrimethylammonio), alkoxy groups (e.g., methoxy)halogen atoms (F, Cl, Br), carboxyl, acyl groups (e.g., formyl), amino,sulfo, aryl groups (e.g., phenyl), aryloxy groups (e.g., phenoxy) andoxo.

[0162] In formula (III) above, n² represents the mol % of the repeatingunit in the range of 1 to 90 mol %. n² is preferably 5 to 80 mol %, morepreferably 10 to 70 mol %.

[0163] Examples of repeating units of formula (III) above are shownbelow.

[0164] Examples of acrylic copolymers containing a repeating unit offormula (III) are shown below. AA means a repeating unit derived fromacrylic acid and MA means a repeating unit derived from methacrylicacid. The proportion of each repeating unit is expressed in mol %.

[0165] PA501: -(AA)₇₀-(III-1)₃₀-

[0166] PA502: -(AA)₆₀-(III-1)₄₀-

[0167] PA503: -(AA)₅₀-(III-1)₅₀-

[0168] PA504: -(AA)₄₀-(III-1)₆₀-

[0169] PA505: -(AA)₆₀-(III-2)₄₀-

[0170] PA506: -(AA)₆₀-(III-3)₄₀-

[0171] PA507: -(AA)₆₀-(III-4)₄₀-

[0172] PA508: -(AA)₆₀-(III-5)₄₀-

[0173] PA509: -(AA)₄₀-(III-6)₄₀-

[0174] PA510: -(AA)₅₀-(III-7)₅₀-

[0175] PA511: -(AA)₇₀-(III-8)₃₀-

[0176] PA512: -(AA)₆₀-(III-9)₄₀-

[0177] PA513: -(AA)₆₀-(III-10)₄₀-

[0178] PA514: -(AA)₆₀-(III-11)₄₀-

[0179] PA515: -(AA)₅₀-(III-12)₅₀-

[0180] PA516: -(AA)₅₀-(III-13)₅₀-

[0181] PA517: -(AA)₇₀-(III-14)₃₀-

[0182] PA518: -(AA)₅₀-(III-15)₅₀-

[0183] PA519: -(AA)₆₀-(III-16)₄₀-

[0184] PA520: -(AA)₆₀-(III-17)₄₀-

[0185] PA521: -(AA)₆₀-(III-18)₄₀-

[0186] PA522: -(AA)₆₀-(III-19)₄₀-

[0187] PA523: -(AA)₇₅-(III-20)₂₅-

[0188] PA524: -(AA)₆₀-(III-20)₄₀-

[0189] PA525: -(AA)₇₀-(III-21)₃₀-

[0190] PA526: -(AA)₈₀-(III-22)₂₀-

[0191] PA527: -(AA)₇₀-(III-22)₃₀-

[0192] PA528: -(AA)₆₀—(III-22)₄₀-

[0193] PA529: -(AA)₇₀-(III-23)₃₀-

[0194] PA530: -(AA)₇₀-(III-24)₃₀-

[0195] PA531: -(AA)₈₀-(III-25)₂₀-

[0196] PA532: -(AA)₇₀-(III-25)₃₀-

[0197] PA533: -(AA)₆₀-(III-25)₄₀-

[0198] PA534: -(AA)₆₀-(III-26)₄₀-

[0199] PA535: -(AA)₇₀-(III-27)₃₀-

[0200] PA536: -(AA)₈₀-(III-28)₂₀-

[0201] PA537: -(AA)₇₀-(III-29)₃₀-

[0202] PA538: -(AA)₆₀-(III-30)₄₀-

[0203] PA539: -(AA)₇₀-(III-31)₃₀-

[0204] PA540: -(AA)₇₀-(III-32)₃₀-

[0205] PA541: -(AA)₆₀-(III-33)₄₀-

[0206] PA542: -(AA)₇₀-(III-34)₃₀-

[0207] PA543: -(AA)₇₀-(III-35)₃₀-

[0208] PA601: -(MA)₇₀-(III-1)₃₀-

[0209] PA602: -(MA)₆₀- (III-1)₄₀-

[0210] PA603: -(MA)₅₀—(III-1)₅₀-

[0211] PA604: -(MA)₄₀-(III-1)₆₀-

[0212] PA605: -(MA)₆₀-(III-2)₄₀-

[0213] PA606: -(MA)₆₀-(III-3)₄₀-

[0214] PA607: -(MA)₆₀- (III-4)₄₀-

[0215] PA608: - (MA)₆₀- (III-5)₄₀-

[0216] PA609: -(MA)₄₀-(III-6)₄₀-

[0217] PA610: -(MA)₅₀-(III-7)₅₀-

[0218] PA611: -(MA)₇₀-(III-8)₃₀-

[0219] PA612: -(MA)₆₀-(III-9)₄₀-

[0220] PA613: -(MA)₆₀-(III-10)₄₀-

[0221] PA614: -(MA)₆₀-(III-11)₄₀-

[0222] PA615: -(MA)₅₀-(III-12)₅₀-

[0223] PA616: -(MA)₅₀-(III-13)₅-

[0224] PA617: -(MA)₇₀- (III-14)₃₀-

[0225] PA618: -(MA)₅₀-(III-15)₅₀-

[0226] PA619: -(MA)₆₀-(III-16)₄₀-

[0227] PA620: -(MA)₆₀-(III-17)₄₀-

[0228] PA621: -(MA)₆₀-(III-18)₄₀-

[0229] PA622: -(MA)₆₀-(III-19)₄₀-

[0230] PA623: -(MA)₇₅-(III-20)₂₅-

[0231] PA624: -(MA)₆₀-(III-20)₄₀-

[0232] PA625: -(MA)₇₀-(III-21)₃₀-

[0233] PA626: -(MA)₈₀-(III-22)₂₀-

[0234] PA627: -(MA)₇₀-(III-22)₃₀-

[0235] PA628: -(MA)₆₀-(III-22)₄₀-

[0236] PA629: -(MA)₇₀-(III-23)₃₀-

[0237] PA630: -(MA)₇₀-(III-24)₃₀-

[0238] PA631: -(MA)₈₀-(III-25)₂₀-

[0239] PA632: -(MA)₇₀-(III-25)₃₀-

[0240] PA633: -(MA)₆₀-(III-25)₄₀-

[0241] PA634: -(MA)₆₀-(III-26)₄₀-

[0242] PA635: -(MA)₇₀-(III-27)₃₀-

[0243] PA636: -(MA)₈₀-(III-28)₂₀-

[0244] PA637: -(MA)₇₀-(III-29)₃₀-

[0245] PA638: -(MA)₆₀-(III-30)₄₀-

[0246] PA639: -(MA)₇₀-(III-31)₃₀-

[0247] PA640: -(MA)₇₀-(III-32)₃₀-

[0248] PA641: -(MA)₆₀-(III-33)₄₀-

[0249] PA642: -(MA)₇₀-(III-34)₃₀-

[0250] PA643: -(MA)₇₀-(III-35)₃₀-

[0251] In formula (IV) above, R³ represents a hydrogen atom or a methylgroup.

[0252] In formula (IV) above, L¹ represents a linking group selectedfrom the group consisting of —NH-alkylene-O—CO—, -alkylene-O—CO—,—O-alkylene-O—CO—, —O-arylene-O-alkylene-O—CO—, —O-arylene-O-alkylene-,—O-arylene-O—, —NH-alkylene-O—CO—, —NH-alkylene-O— and —NH-alkylene-,preferably —NH-alkylene-O—CO—, -alkylene-O—CO—, -O-alkylene-O—CO—,-O-arylene-O-alkylene-O—CO—, —O-arylene-O— and —NH-alkylene-O—CO—,especially —NH-alkylene-O—CO—.

[0253] The alkylene group may be branched or may have a cyclicstructure. The alkylene group preferably contains 1 to 30, morepreferably 1 to 20, still more preferably 1 to 15, most preferably 1 to12 carbon atoms.

[0254] The arylene group is preferably a phenylene or a naphthylene,more preferably a phenylene, most preferably a p-phenylene. The arylenegroup may be substituted. Examples of substituents for the arylene groupare as mentioned earlier for the arylene group.

[0255] In formula (IV) above, Q represents a polymerizable group. Thepolymerizable group is preferably similar to the polymerizable group (O)of the liquid crystal molecule, as described above. Specifically, Q ispreferably an unsaturated polymerizable group, an epoxy group or anaziridinyl group, more preferably an ethylenically unsaturatedpolymerizable group.

[0256] In formula (IV) above, p represents the mol % of the repeatingunit in the range of 0.1 to 20 mol %. p is preferably 0.1 to 10 mol %,more preferably 3 to 5 mol %.

[0257] Examples of repeating units having a polymerizable group in theside chain are shown below.

[0258] When a repeating unit having a polymerizable group in the sidechain is introduced into an acrylic copolymer, the acrylic copolymerpreferably contains the repeating unit having a polymerizable group inthe side chain in the range of 0.1 to 10 mol %, more preferably 3 to 5mol %.

[0259] In addition to the acrylic orthogonal alignment layers describedabove, alignment layers based on polyvinyl alcohols as disclosed in thespecification of JP-A 2002-062427 or polyamic acids as disclosed in JP-A2001-254481 may also be used.

[0260] Then, a second alignment layer is formed and a second opticallyanisotropic liquid crystal layer is formed on the second alignmentlayer.

[0261] Materials and methods for forming the second alignment layer arenot specifically limited so far as an alignment layer capable ofhomogenously aligning the rod-like liquid crystal compound in the secondoptically anisotropic layer is obtained. For example, the alignmentlayer can be formed from various materials by various methods such assubjecting a film of an organic compound (preferably a polymer) to arubbing treatment, obliquely depositing an inorganic compound, forming alayer having microgrooves, or accumulating an organic compound (e.g.,ω-trichosanic acid, dioctadecylmethylammonium chloride, methyl stearate)by Langmuir-Blodgett method (LB film). Alignment layers producing analignment effect under an electric or magnetic field or irradiation arealso known.

[0262] Especially, the second alignment layer is preferably formed bysubjecting a film of a polymer to a rubbing treatment. The rubbingtreatment is performed by rubbing the surface of the polymer layer in adirection several times with paper or a cloth. For example, a polymersolution is applied to the surface of the first optically anisotropiclayer and dried to form a film, which is then subjected to a rubbingtreatment to form a second alignment layer. In the present invention,the second alignment layer can be formed by a rubbing treatment in adirection at an angle of substantially 15° with respect to thelongitudinal direction of the transparent substrate. That is, the secondalignment layer can be formed by a rubbing process in such a manner thatthe angle between the rubbing axis and the longitudinal direction of thetransparent substrate is substantially 15°. A coating solutioncontaining a rod-like liquid crystal compound is applied to thus formedsecond orthogonal alignment layer, and the rod-like liquid crystalcompound is aligned so that the liquid crystal molecules are aligned ina direction substantially parallel to the rubbing axis of the alignmentlayer. That is, the rod-like liquid crystal compound can be aligned in adirection at an angle of 15° with respect to the longitudinal directionof the transparent substrate to form a second optically anisotropiclayer having a phase shift of π/2.

[0263] The type of the polymer used for the second alignment layer isdetermined depending on the alignemetn (especially, average tilt angle)of the rod-like liquid crystal compound used in the second opticallyanisotropic layer.

[0264] In order to homogenously align the liquid crystal compound (at anaverage tilt angle of 0 to 50°), a polymer that does not lower thesurface energy of the alignment layer (a normal polymer for alignmentlayers) is used. Specific types of suitable polymers are described invarious documents relating to liquid crystal cells or opticalcompensation sheets.

[0265] The thickness of the second alignment layer is preferably 0.01 to5 μm, more preferably 0.05 to 1 μm.

[0266] The second alignment layer may be formed on a temporary substrateand the second optically anisotropic layer may be formed by aligning theliquid crystal compound in the second optically anisotropic layer andthen transferred onto the transparent substrate (or onto the firstoptically anisotropic layer). The liquid crystal compound fixed in analignment can remain the alignment without alignment layer. The firstoptically anisotropic layer and the second optically anisotropic layerare laminated in such a manner that in-plane axes a1 and a2 aresubstantially parallel to each other and that the angle between the slowaxis of the first optically anisotropic layer and the slow axis of thesecond optically anisotropic layer is substantially 60° where a1 meansthe in-plane axis parallel to the longitudinal direction of thesubstrate (or temporary substrate) on which the first opticallyanisotropic layer is formed and a2 means the in-plane axis parallel tothe longitudinal direction of the temporary substrate (or transparentsubstrate) on which the second optically anisotropic layer is formed.

[0267] The second alignment layer may not be necessary if the rod-likeliquid crystal compound in the second optically anisotropic layer isstably aligned at a desired angle. For the purpose of improving adhesionbetween the liquid crystal compound and the transparent substrate, analignment layer, such as described in JP-A 1997-152509, forming achemical bond with liquid crystal molecules at the interface may beused, and the rubbing treatment may not be performed when an alignmentlayer is only used for the purpose of improving adhesion.

[0268] In addition to at least one rod-like liquid crystal compound, thefirst optically anisotropic layer and the second optically anisotropiclayer preferably further contain an agent for promoting liquid crystalalignment, especially represented by formula (V) below:

(Hb-L²-)_(n)B¹  Formula (V)

[0269] wherein Hb represents an aliphatic group containing 6 to 40carbon atoms or an aliphatic-substituted oligosiloxanoxy groupcontaining 6 to 40 carbon atoms. Hb preferably represents an aliphaticgroup containing 6 to 40 carbon atoms, more preferably afluorine-substituted aliphatic group containing 6 to 40 carbon atoms ora branched aliphatic group containing 6 to 40 carbon atoms, mostpreferably a fluorine-substituted alkyl group containing 6 to 40 carbonatoms or a branched alkyl group containing 6 to 40 carbon atoms.

[0270] The aliphatic group is more preferably a linear aliphatic groupthan a cyclic aliphatic group. The linear aliphatic group may bebranched. The aliphatic group preferably contains 7 to 35, morepreferably 8 to 30, still more preferably 9 to 25, most preferably 10 to20 carbon atoms.

[0271] The aliphatic group includes alkyl, substituted alkyl, alkenyl,substituted alkenyl, alkynyl and substituted alkynyl groups, preferablyalkyl, substituted alkyl, alkenyl and substituted alkenyl groups, morepreferably alkyl and substituted alkyl groups.

[0272] Examples of substituents for the aliphatic group include halogenatoms, hydroxyl, cyano, nitro, alkoxy groups, substituted alkoxy groups(e.g., oligoalkoxy), alkenyloxy groups (e.g., vinyloxy), acyl groups(e.g., acryloyl, methacryloyl), acyloxy groups (e.g., acryloyloxy,benzoyloxy), sulfamoyl, aliphatic-substituted sulfamoyl groups andepoxyalkyl groups (e.g., epoxyethyl), preferably halogen atoms, morepreferably a fluorine atom. In fluorine-substituted aliphatic groups,the proportion of fluorine atom substituted for the hydrogen atom in thealiphatic group is preferably 50 to 100%, more preferably 60 to 100%,still more preferably 70 to 100%, further more preferably 80 to 100%,most preferably 85 to 100%.

[0273] The aliphatic-substituted oligosiloxanoxy group preferablycontains 7 to 35, more preferably 8 to 30, still more preferably 9 to25, most preferably 10 to 20 carbon atoms. The aliphatic-substitutedoligosiloxanoxy group is represented by the formula below:

R¹—(Si(R²)₂—O)_(q)—

[0274] wherein R¹ represents a hydrogen atom, hydroxyl or an aliphaticgroup; R² represents a hydrogen atom, an aliphatic group or an alkoxygroup; and q represents an integer of any of 1 to 12. The aliphaticgroups represented by R¹ and R² are more preferably linear aliphaticgroups than cyclic aliphatic groups. The linear aliphatic groups may bebranched. The aliphatic groups preferably contain 1 to 12, morepreferably 1 to 8, still more preferably 1 to 6, especially 1 to 4carbon atoms.

[0275] The aliphatic groups represented by R¹ and R² include alkyl,substituted alkyl, alkenyl, substituted alkenyl, alkynyl and substitutedalkynyl groups, preferably alkyl, substituted alkyl, alkenyl andsubstituted alkenyl groups, more preferably alkyl and substituted alkylgroups.

[0276] The aliphatic groups represented by R¹ and R² may be substitutedby halogen atoms, hydroxyl, cyano, nitro, alkoxy groups, substitutedalkoxy groups (e.g., oligoalkoxy), alkenyloxy groups (e.g., vinyloxy),acyl groups (e.g., acryloyl, methacryloyl), acyloxy groups (e.g.,acryloyloxy, benzoyloxy), sulfamoyl, aliphatic-substituted sulfamoylgroups and epoxyalkyl groups (e.g., epoxyethyl).

[0277] The alkoxy group represented by R may be branched or may have acyclic structure. The alkoxy group preferably contains 1 to 12, morepreferably 1 to 8, still more preferably 1 to 6, further more preferably1 to 4 carbon atoms.

[0278] Examples of Hb are shown below.

[0279] Hb1: n-C₁₆H₃₃—

[0280] Hb2: n-C₂₀H₄₁—

[0281] Hb3 n-C₆H₁₃—CH(n-C₄H₉)—CH₂—CH₂—

[0282] Hb4: n-C₁₂H₂₅—

[0283] Hb5: n-C₁₈H₃₇—

[0284] Hb6: n-C₁₄H₂₉—

[0285] Hb7: n-C₁₅H₃₁—

[0286] Hb8: n-C₁₀H₂₁—

[0287] Hb9: n-C₁₀H₂₁—CH(n-C₄H₉)—CH₂—CH₂—

[0288] Hb10: n-C₈F₁₇—

[0289] Hb11: n-C₈H₁₇—

[0290] Hb12: CH(CH₃)₂—{C₃H₆—CH(CH₃)}₃—C₂H₄—

[0291] Hb13: —CH(CH₃)₂—{C₃H₆—CH(CH₃)}₂—C₃H₆—C(CH₃)═CH—CH₂—

[0292] Hb14: n-C₈H₁₇—CH (n-C₆H₁₃)—CH₂—CH₂—

[0293] Hb15: n-C₆H₁₃—CH(C₂H₅)—CH₂—CH₂—

[0294] Hb16: n-C₈F₁₇—CH(n-C₄F₉)—CH₂—

[0295] Hb17: n-C₈F₁₇—CF(n-C₆F₁₃)—CF₂—CF₂—

[0296] Hb18: n-C₃F₇—CF(CF₃)—CF₂—

[0297] Hb19: Si(CH₃)₃—{Si(CH₃)₂—O}₆—O—

[0298] Hb20: Si(OC₃H₇)(C₁₆F₃₃)(C₂H₄—SO₂—NH—C₈F₁₇)—O—

[0299] In formula (V) above, L² represents a single bond or a divalentlinking group. The divalent linking group is preferably a group selectedfrom the group consisting of -alkylene-, -fluorine-substitutedalkylene-, —O—, —S—, —CO—, —NR—, —SO₂— and combinations thereof. Rrepresents a hydrogen atom or an alkyl group containing 1 to 20 carbonatoms. More preferably, L^(1A) represents a divalent linking groupselected from the group consisting of -alkylene-, —O—, —S—, —CO—, —NR—,—SO₂— and combinations thereof. R preferably represents a hydrogen atomor an alkyl group containing 1 to 20 carbon atoms, more preferably ahydrogen atom or an alkyl group containing 1 to 15 carbon atoms, mostpreferably a hydrogen atom or an alkyl group containing 1 to 12 carbonatoms.

[0300] The alkylene group or fluorine-substituted alkylene grouppreferably contains 1 to 40, more preferably 1 to 30, still morepreferably 1 to 20, further more preferably 1 to 15, most preferably 1to 12 carbon atoms.

[0301] Examples of L² are shown below. The left side is bonded to Hb andthe right side is bonded to B¹.

[0302] L¹⁰: — (a single bond)

[0303] L¹¹: —O—

[0304] L¹²: —O—CO—

[0305] L¹³: —CO—C₄H₈—O—

[0306] L¹⁴: —O—C₂H₄—O—C₂H₄—O—

[0307] L¹⁵: —S—

[0308] L¹⁶: —N(n-C₁₂H₂₅)—

[0309] L¹⁷: —SO₂—N(n-C₃H₇)—CH₂CH₂—O—

[0310] L¹⁸: —O-{CF(CF₃)—CF₂—O}₃—CF(CF₃)—

[0311] In formula (V) above, n represents an integer of any of 2 to 12.n preferably represents an integer of any of 2 to 9, more preferably aninteger of any of 2 to 6, still more preferably 2, 3 or 4, mostpreferably 3 or 4.

[0312] In formula (V) above, B¹ represents an n-valent group having anexcluded volume effect containing at least three cyclic structures. B¹preferably represents an n-valent group of formula (V-a) below.

(-Cy¹-L³-)_(n)Cy²  Formula (V-a)

[0313] wherein Cy¹ represents a divalent cyclic group. Cy¹ preferablyrepresents a divalent aromatic hydrocarbon group or a divalentheterocyclic group, more preferably a divalent aromatic hydrocarbongroup.

[0314] The aromatic hydrocarbon group means arylene groups andsubstituted arylene groups.

[0315] Examples of arylene groups include phenylene, indenylene,naphthylene, fluorenylene, phenanthrenylene, anthrylene and pyrenylenegroups, preferably phenylene and naphthylene groups.

[0316] Examples of substituted arylene groups include aliphatic groups,aromatic hydrocarbon groups, heterocyclic group, halogen atoms, alkoxygroups (e.g., methoxy, ethoxy, methoxyethoxy), aryloxy groups (e.g.,phenoxy), arylazo groups (e.g., phenylazo), alkylthio groups (e.g.,methylthio, ethylthio, propylthio), alkylamino groups (e.g.,methylamino, propylamino), acyl groups (e.g., acetyl, propanoyl,octanoyl, benzoyl) acyloxy groups (e.g., acetoxy, pivaloyloxy,benzoyloxy), hydroxy, mercapto, amino, carboxyl, sulfo, carbamoyl,sulfamoyl and ureido.

[0317] When another aromatic hydrocarbon ring is bonded to the divalentaromatic hydrocarbon group as a substituent via a single bond, vinylenebond or ethynylene bond, a specific effect of promoting liquid crystalalignment is obtained as described above.

[0318] It may also have a group corresponding to Hb-L²- as asubstituent.

[0319] The divalent heterocyclic group represented by Cy¹ preferably hasa 5-membered, 6-membered or 7-membered heterocycle, more preferably a5-membered or 6-membered heterocycle, most preferably a 6-memberedheterocycle. Heteroatoms contained in the heterocycle are preferablynitrogen, oxygen and sulfur atoms. The heterocycle is preferably anaromatic heterocycle. The aromatic heterocycle is typically anunsaturated heterocycle, more preferably an unsaturated heterocyclehaving the maximum number of double bonds. Examples of heterocyclesinclude furan, thiophene, pyrrole, pyrroline, pyrrolidine, oxazole,isoxazole, thiazole, isothiazole, imidazole, imidazoline, imidazolidine,pyrazole, pyrazoline, pyrazolidine, triazole, furazane, tetrazole,pyran, thiine, pyridine, piperdine, oxazine, morpholine, thiazine,pyridazine, pyrimidine, pyrazine, piperazine and triazine rings.

[0320] The heterocycle may be condensed to another heterocycle, analiphatic ring or an aromatic hydrocarbyl ring. Examples of condensedheterocycles include benzofuran, isobenzofuran, benzothiophene, indole,indoline, isoindole, benzoxazole, benzothiazole, indazole,benzimidazole, chromene, chromane, isochromane, quinoline, isoquinoline,cinnoline, phthalazine, quinazoline, quinoxaline, dibenzofuran,carbazole, xanthene, acridine, phenanthridine, phenanthroline,phenazine, phenoxazine, thianthrene, indolizine, quinolizine,quinuclidine, naphthyridine, purine and pteridine rings.

[0321] The divalent heterocyclic group may have a substituent. Examplesof substituents are as mentioned for the substituted arylene group.

[0322] The divalent heterocyclic group may be bonded to L³ or the cyclicgroup (Cy²) at the center of the molecule (when L³ is a single bond) viaa heteroatom (e.g., a nitrogen atom in a piperidine ring). Attachedheteroatoms may form an onium salt (e.g., an oxonium, sulfonium orammonium salt).

[0323] The cyclic structures of Cy¹ and Cy² described below may form aplanar structure as a whole. When the cyclic structures form planarstructures (i.e. disc-like structures) as a whole, a specific effect ofpromotong liquid crystal alignment is obtained as described above.

[0324] Examples of Cy¹ are shown below. When a plurality of groupscorresponding to Hb-L²- are bonded to a divalent aromatic hydrocarbylgroup or a divalent heterocyclic group, any one is Hb-L²- defined in theformula above and the others are substituents for the divalent aromatichydrocarbyl group or the divalent heterocyclic group.

[0325] In formula (V-a) above, L³ represents a single bond or a divalentlinking group selected from the group consisting of -alkylene-,-alkenylene-, -alkynylene-, —O—, —S—, —CO—, —NR—, —SO₂— and combinationsthereof. R represents a hydrogen atom or an alkyl group containing 1 to30 carbon atoms. L³ preferably represents a divalent linking groupselected from the group consisting of —O—, —S—, —CO—, —NR—, —SO₂— andcombinations thereof. R is preferably a hydrogen atom or an alkyl groupcontaining 1 to 20 carbon atoms, more preferably a hydrogen atom or analkyl group containing 1 to 15 carbon atoms, most preferably a hydrogenatom or an alkyl group containing 1 to 12 carbon atoms.

[0326] The alkylene group preferably contains 1 to 40, more preferably 1to 30, still more preferably 1 to 20, further more preferably 1 to 15,most preferably 1 to 12 carbon atoms.

[0327] The alkenylene or alkynylene group preferably contains 2 to 40,more preferably 2 to 30, still more preferably 2 to 20, further morepreferably 2 to 15, most preferably 2 to 12 carbon atoms.

[0328] Examples of L³ are shown below. The left side is bonded to Cy¹and the right side is bonded to Cy².

[0329] L²⁰: — (a single bond)

[0330] L²¹: —S—

[0331] L²²: —NH—

[0332] L²³: —NH—SO₂—NH—

[0333] L²⁴: —NH—CO—NH—

[0334] L²⁵: —SO₂—

[0335] L²⁶: —O—NH—

[0336] L²⁷: —C≡C—

[0337] L²⁸: —CH═CH—S—

[0338] L²⁹: —CH₂—O—

[0339] L³⁰: —N(CH₃)—

[0340] L³¹: —CO—O—

[0341] In formula (V-a) above, n represents an integer of any of 2 to12. n is preferably an integer of any of 2 to 9, more preferably aninteger of any of 2 to 6, still more preferably 2, 3 or 4, mostpreferably 3 or 4.

[0342] In formula (V-a) above, Cy² represents an n-valent cyclic group.Cy² is preferably an n-valent aromatic hydrocarbon group or an n-valentheterocyclic group.

[0343] Examples of the aromatic hydrocarbon ring in the aromatichydrocarbon group represented by Cy² include benzene, indene,naphthalene, fluorene, phenanthrene, anthracene and pyrene rings,preferably benzene and naphthalene rings, especially a benzene ring.

[0344] The aromatic hydrocarbon group represented by Cy² may besubstituted. Examples of substituents include aliphatic groups, aromatichydrocarbon groups, heterocyclic groups, halogen atoms, alkoxy groups(e.g., methoxy, ethoxy, methoxyethoxy), aryloxy groups (e.g., phenoxy),arylazo groups (e.g., phenylazo), alkylthio groups (e.g., methylthio,ethylthio, propylthio), alkylamino groups (e.g., methylamino,propylamino), arylamino groups (e.g., phenylamino), acyl groups (e.g.,acetyl, propanoyl, octanoyl, benzoyl), acyloxy groups (e.g., acetoxy,pivaloyloxy, benzoyloxy), and hydroxy, mercapto, amino, carboxyl, sulfo,carbamoyl, sulfamoyl and ureido.

[0345] The heterocyclic group represented by Cy² preferably has a5-membered, 6-membered or 7-membered heterocycle, more preferably a5-membered or 6-membered heterocycle, most preferably a 6-memberedheterocycle. Heteroatoms contained in the heterocycle are preferablynitrogen, oxygen and sulfur atoms. The heterocycle is preferably anaromatic heterocycle. The aromatic heterocycle is typically anunsaturated heterocycle, more preferably an unsaturated heterocyclehaving the maximum number of double bonds. Examples of the heterocycleinclude furan, thiophene, pyrrole, pyrroline, pyrrolidine, oxazole,isoxazole, thiazole, isothiazole, imidazole, imidazoline, imidazolidine,pyrazole, pyrazoline, pyrazolidine, triazole, furazane, tetrazole,pyran, thiine, pyridine, piperidine, oxazine, morpholine, thiazine,pyridazine, pyrimidine, pyrazine, piperazine and triazine rings,preferably a triazine ring, especially a 1,3,5-triazine ring.

[0346] The heterocycle may be condensed to another heterocycle, analiphatic ring or an aromatic hydrocarbyl ring. However, monocyclicheterocycles are preferred.

[0347] Examples of Cy² are shown below.

[0348] Agents for promoting liquid crystal alignment are compoundsobtained by combining a hydrophobic group (Hb), a linking group (L²) anda group having an excluded volume effect (B¹) described above. Thesecombinations are not specifically limited.

[0349] Examples of agents for promoting liquid crystal alignmentrepresented by formula (V) above are shown below.

[0350] The first and second optically anisotropic layers of the presentinvention contain at least one rod-like liquid crystal compound. In thefirst and second optically anisotropic layers, the molecules of therod-like liquid crystal compound are preferably substantially uniformlyaligned, more preferably fixed in a substantially uniformly alignedstate, and the liquid crystal molecules are most preferably fixed bypolymerization reaction. The alignment of the liquid crystal moleculesis adjusted so that the angle between the slow axis in the plane of theoptically anisotropic layer and the longitudinal direction of thetransparent substrate is substantially 75° or 15°. The liquid crystalmolecules are preferably homogenously aligned (homogeneous alignment).As used herein, “substantially” means ±5°, preferably ±4°. For example,substantially 75° means 75±5°. Preferably used rod-like liquid crystalcompounds are azomethines, azoxys, cyanobiphenyls, cyanophenyl esters,benzoic acid esters, cyclohexanecarboxylic acid phenyl esters,cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines,alkoxy-substituted phenylpyrimidines, phenyl dioxanes, tolans andalkenylcyclohexyl benzonitriles. Not only low molecular liquid crystalcompounds as mentioned above but also high molecular liquid crystalcompounds can be used.

[0351] Suitable rod-like liquid crystal compounds include thosedescribed in “Makromol. Chem., Vol. 190, p. 2255(1989)”; “AdvancedMaterials Vol. 5, p. 107 (1993)”; U.S. Pat. Nos. 4,683,327, 5,622,648and 5,770,107; International Publications WO95/22,586, WO95/24,455,WO97/00,600, WO98/23,580 and WO98/52905; JP-A 1989-272551, JP-A1994-16616, JP-A 1995-110469 and JP-A 1999-80081; and Japanese PatentApplication No. 2001-64627, more preferably, compounds of formula (VI)below:

Q¹¹-L¹¹-Cy¹¹-L¹²-(Cy¹²-L¹³)_(n)-Cy¹³-L¹⁴-Q¹²  Formula (VI)

[0352] wherein Q¹¹ and Q¹² independently represent a polymerizablegroup; L¹¹ and L¹⁴ independently represent a divalent linking group; L¹²and L¹³ independently represent a single bond or a divalent linkinggroup; Cy¹¹, Cy¹² and Cy¹³ independently represent a divalent cyclicgroup; and n represents 0, 1 or 2.

[0353] In formula (VI) above, Q¹¹ and Q¹² independently represent apolymerizable group. The polymerization reaction of the polymerizablegroup is preferably addition polymerization (including ring openingpolymerization) or condensation polymerization. In other words, thepolymerizable group is preferably a functional group responsible foraddition polymerization reaction or condensation polymerizationreaction. Examples of polymerizable groups are shown below.

[0354] The polymerizable group (Q¹¹ and Q¹²) is preferably anunsaturated polymerizable group (Q-1 to Q-7), an epoxy group (Q-8) or anaziridinyl group (Q-9), more preferably an unsaturated polymerizablegroup, most preferably an ethylenically unsaturated polymerizable group(Q-1 to Q-6).

[0355] L¹¹ and L¹⁴ independently represent a divalent linking group.Preferably, L¹¹ and L¹⁴ independently represent a divalent linking groupselected from the group consisting of —O—, —S—, —CO—, —NR¹²—, divalentlinear groups, divalent cyclic groups and combinations thereof whereinR¹² represents an alkyl group containing 1 to 7 carbon atoms or ahydrogen atom. R¹² preferably represents an alkyl group containing 1 to4 carbon atoms or a hydrogen atom, more preferably a methyl group, anethyl group or a hydrogen atom, most preferably a hydrogen atom.Examples of divalent linking groups consisting of combinations are shownbelow. Here, the left side is bonded to Q (Q¹¹ or Q¹²) and the rightside is bonded to Cy (Cy¹¹ or Cy¹³).

[0356] L-1: —CO—O-“divalent linear group”-O—

[0357] L-2: —CO—O-“divalent linear group”-O-“divalent cyclicgroup”-CO—O—

[0358] L-3: —CO—O-“divalent linear group”-O-“divalent cyclicgroup”-O—CO—

[0359] L-4: —CO—O-“divalent linear group”-O-“divalent cyclicgroup”-“divalent linear group”-

[0360] L-5: —CO—O-“divalent linear group”-O-“divalent cyclic group”-

[0361] L-6: —CO—O-“divalent linear group”-O-“divalent cyclicgroup”-“divalent linear group”-CO—O—

[0362] L-7: —CO—O-“divalent linear group”-O-“divalent cyclicgroup”-O—CO-“divalent linear group”-.

[0363] The divalent linear group contained in the divalent linking grouprepresented by L¹¹ and L¹⁴ means an alkylene, substituted alkylene,alkenylene, substituted alkenylene, alkynylene or substituted alkynylenegroup. Preferred are alkylene, substituted alkylene, alkenylene andsubstituted alkenylene groups, more preferably alkylene and alkenylenegroups.

[0364] The alkylene group may be branched. The alkylene group preferablycontains 1 to 12, more preferably 2 to 10, most preferably 3 to 8 carbonatoms.

[0365] The alkylene moiety of the substituted alkylene group is asdefined above for the alkylene group. Examples of substituents for thesubstituted alkylene group include halogen atoms.

[0366] The alkenylene group may be branched. The alkenylene grouppreferably contains 2 to 12, more preferably 2 to 8, most preferably 2to 4 carbon atoms.

[0367] The alkenylene moiety of the substituted alkenylene group is asdefined above for the alkenylene group. Examples of substituents for thesubstituted alkenylene group include halogen atoms.

[0368] The alkynylene group may be branched. The alkynylene grouppreferably contains 2 to 12, more preferably 2 to 8, most preferably 2to 4 carbon atoms.

[0369] The alkynylene moiety of the substituted alkynylene group is asdefined above for the alkynylene group. Examples of substituents for thesubstituted alkynylene group include halogen atoms.

[0370] The definition and examples of the divalent cyclic groupcontained in the divalent linking group represented by L¹¹ and L¹⁴ aresimilar to the definition and examples of Cy¹¹, Cy¹² and Cy¹³ below.

[0371] In formula (VI) above, L¹² and L¹³ independently represent asingle bond or a divalent linking group. L¹² and L¹³ independentlyrepresent a divalent linking group selected from the group consisting of—O—, —S—, —CO—, —NR¹²—, divalent linear groups, divalent cyclic groupsand combinations thereof or a single bond wherein R¹² represents analkyl group containing 1 to 7 carbon atoms or a hydrogen atom,preferably an alkyl group containing 1 to 4 carbon atoms or a hydrogenatom, more preferably a methyl group, an ethyl group or a hydrogen atom,most preferably a hydrogen atom. The divalent linear group and divalentcyclic group contained in the divalent linking group represented by L¹²and L¹³ are as defined for L¹¹ and L¹⁴.

[0372] In formula (VI) above, n represents 0, 1 or 2. When n is 2, twoL³s may be identical or different, and two Cy¹²s may also be identicalor different. n is preferably 1 or 2, more preferably 1.

[0373] In formula (VI) above, Cy¹¹, Cy¹² and Cy¹³ independentlyrepresent a divalent cyclic group.

[0374] The ring contained in the cyclic group is preferably a5-membered, 6-membered or 7-membered ring, more preferably a 5-memberedor 6-membered ring, most preferably a 6-membered ring. The ringcontained in the cyclic group may be a condensed ring, but a monocycleis more preferred.

[0375] The ring contained in the cyclic group may be any of aromaticrings, aliphatic rings and heterocycles. Examples of aromatic ringsinclude benzene and naphthalene rings. Examples of aliphatic ringsinclude a cyclohexane ring. Examples of heterocycles include pyridineand pyrimidine rings.

[0376] Cyclic groups having a benzene ring preferably include a1,4-phenylene group. Cyclic groups having a naphthalene ring preferablyinclude a naphthalene-1,5-diyl group and a naphthalene-2,6-diyl group.Cyclic groups having a pyridine ring preferably include apyridine-2,5-diyl group. Cyclic groups having a pyrimidine ringpreferably include a pyrimidine-2,5-diyl group.

[0377] The cyclic group is preferably a 1,4-phenylene group or a1,4-cyclohexylene group.

[0378] The cyclic group may be substituted. Examples of substituentsinclude halogen atoms, cyano, nitro, alkyl groups containing 1 to 5carbon atoms, halogen-substituted alkyl groups containing 1 to 5 carbonatoms, alkoxy groups containing 1 to 5 carbon atoms, alkylthio groupscontaining 1 to 5 carbon atoms, acyl groups containing 1 to 5 carbonatoms, acyloxy groups having 2 to 6 carbon atoms, alkoxycarbonyl groupshaving 2 to 6 carbon atoms, carbamoyl, alkyl-substituted carbamoylgroups having 2 to 6 carbon atoms and amide groups having 2 to 6 carbonatoms.

[0379] Examples of polymerizable liquid crystal compounds of formula(VI) above are shown below.

[0380] The first and second optically anisotropic layers can be formedby applying a coating solution containing rod-like liquid crystalmolecules and a polymerization initiator as described below or otheradditives to the first and second alignment layers, respectively. Thesolvent used for preparing the coating solution is preferably an organicsolvent. Examples of organic solvents include amides (e.g., N,N-dimethylformamide), sulfoxides (e.g., dimethyl sulfoxide), heterocycliccompounds (e.g., pyridine), hydrocarbons (e.g., benzene, hexane), alkylhalides (e.g., chloroform, dichloromethane), esters (e.g., methylacetate, butyl acetate), ketones (e.g., acetone, methyl ethyl ketone)and ethers (e.g., tetrahydrofuran, 1,2-dimethoxyethane) Alkyl halidesand ketones are preferred. Two or more organic solvents may be used incombination. The coating solution can be applied by known techniques(e.g., extrusion coating, direct gravure coating, reverse gravurecoating, die coating).

[0381] Aligned liquid crystal molecules are fixed in the alignment,preferably by the polymerization reaction of the polymerizable group (P)introduced into the liquid crystal molecules. The polymerizationreaction includes thermal polymerization reaction using a thermalpolymerization initiator and photo-polymerization reaction using aphoto-polymerization initiator. Photo-polymerization reaction ispreferred. Examples of photo-polymerization initiators includeα-carbonyl compounds (described in U.S. Pat. Nos. 2,367,661 and2,367,670), acyloin ethers (described in U.S. Pat. No. 2,448,828)α-hydrocarbon-substituted aromatic acyloin compounds (described in U.S.Pat. No. 2,722,512), polynuclear quinone compounds (described in U.S.Pat. Nos. 3,046,127 and 2,951,758), combinations of triarylimidazoledimers and p-aminophenyl ketone (described in U.S. Pat. No. 3,549,367),acridine and phenazine compounds (described in JP-A 1985-105667 and U.S.Pat. No. 4,239,850) and oxadiazole compounds (described in U.S. Pat. No.4,212,970).

[0382] The amount of the photo-polymerization initiators to be used ispreferably 0.01 to 20% by weight, more preferably 0.5 to 5% by weight onthe basis of solids in the coating solution. Irradiation forpolymerizing the liquid crystal molecules preferably uses UV rays. Theirradiation energy is preferably 20 mJ/cm² to 50 J/cm², more preferably100 to 800 mJ/cm². Irradiation may be performed with heating toaccelerate the photo-polymerization reaction.

[0383] The thicknesses of the first and second optically anisotropiclayers are preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm.

[0384] Suitable materials for the transparent substrate include, but notspecifically limited to, glass plates or polymer films, among whichpolymer films are preferred to obtain light-weight thin-layer products.Especially, polymer films with low wavelength dispersion are preferablyused. The transparent substrate preferably has a small opticalanisotropy. Here, the transparent substrate means that it has atransmittance of 80% or more. Preferably, the low wavelength dispersionspecifically means an Re400/Re700 ratio of less than 1.2. Preferably,the small optical anisotropy specifically means an in-plane retardation(Re) of 20 nm or less, more preferably 10 nm or less. The longtransparent substrate has the form of a roll or a rectangular sheet.Preferably, the first and second optically anisotropic layers arelaminated on a transparent substrate in the form of a roll, which isthen cut into a desired size.

[0385] Examples of polymers include cellulose esters, polycarbonates,polysulfones, polycycloolefin, polyether sulfones, polyacrylates andpolymethacrylates, preferably cellulose esters, more preferably acetylcellulose, most preferably triacetyl cellulose. The polymer films arepreferably formed by solvent casting. The thickness of the transparentsubstrate is preferably 20 to 500 μm, more preferably 50 to 200 μm. Thetransparent substrate may be subjected to a surface treatment (e.g.,glow discharge treatment, corona discharge treatment, UV treatment,flame treatment) to improve adhesion between the transparent substrateand the overlying layer (an adhesive layer, orthogonal alignment layeror optically anisotropic layer). An adhesive layer (undercoat layer) maybe provided on the transparent substrate.

[0386] Although the foregoing description relates to embodiments ofretarders in which incident light is right-handed circularly polarizedlight for convenience of explanation, it will be appreciated that thepresent invention also includes embodiments for left-handed circularlypolarized light. In an embodiment for left-handed circularly polarizedlight, a first optically anisotropic layer having a phase shift of π anda second optically anisotropic layer having a phase shift of π/2 arelaminated on a long transparent substrate in such a manner that thelongitudinal direction of the substrate forms an angle of −75° with theslow axis of the first optically anisotropic layer and an angle of −15°with the slow axis of the second optically anisotropic layer. Retardersof this embodiment can be prepared by being the rubbing axis of thefirst alignment layer at 15° and the rubbing axis of the secondalignment layer at −15° with respect to the longitudinal direction ofthe transparent substrate.

[0387] Retarders of the present invention can be especiallyadvantageously used as λ/4 plates in reflective liquid crystal displaydevices, λ/4 plates in pickups for writing on optical discs, or λ/4plates in anti-reflection coatings. Typically, λ/4 plates are used ascircular polarizers in combination with polarizing films. Thus,retarders can be easily incorporated into intended devices such asreflective liquid crystal display devices when they are combined withpolarizing films to form circular polarizers. Retarders of the presentinvention can be used in combination with polarizing films in reflectiveliquid crystal display devices to reduce blueness when a black image isdisplayed. Moreover, retarders of the present invention can be storedand transported in the form of a roll and can be continuously treated ina roll-to-roll manner during lamination to polarizing films, so thatthey can be easily prepared into circular polarizers.

[0388] Circular polarizers of the present invention comprise apolarizing film in addition to a retarder of the present invention. Thepolarizing film is laminated at the bottom the transparent substrate (onthe side opposite to the first and second optically anisotropic layers)in such a manner that the longitudinal direction of the transparentsubstrate substantially coincides with the absorption axis. That is,circular polarizers of the present invention have a polarizing filmhaving a polarization axis in a direction substantially perpendicular tothe longitudinal direction of the transparent substrate.

[0389] Polarizing films used in the present invention includeiodine-based polarizing films, dye-based polarizing films using dichroicdyes and polyene-based polarizing films. Iodine-based polarizing filmsand dye-based polarizing films are typically prepared with polyvinylalcohol-based films. The transmission axis of the polarizing filmcorresponds to the direction perpendicular to the orientation directionof the film. The polarizing film typically has a protective film on eachside. In the present invention, however, the transparent substrate canserve as a protective film on one side of the polarizing film. When aseparate protective film is used other than the transparent substrate,it is preferably a cellulose ester film having high optical isotropy,especially a triacetyl cellulose film.

[0390] Circular polarizers of the present invention serve as broadbandλ/4 plates. The broadband λ/4 plates here specifically mean that theyhave a retardation value/wavelength ratio within the range of 0.2 to 0.3measured at a wavelength of any of 450 nm, 550 nm and 650 nm. Theretardation value/wavelength ratio is preferably within the range of0.21 to 0.29, more preferably within the range of 0.22 to 0.28, stillmore preferably within the range of 0.23 to 0.27, most preferably withinthe range of 0.24 to 0.26.

EXAMPLES

[0391] The present invention will further be detailed referring tospecific Examples. It is to be noted that any materials, reagents,ratios of use thereof and operations shown in the Examples below canproperly be modified without departing from the spirit of the presentinvention. Thus the present invention is by no means limited to theExamples described below.

Example 1

[0392] (Formation of an Alignment Layer)

[0393] An optically isotropic triacetyl cellulose film in the form of aroll of 100 μm in thickness, 500 mm in width and 500 m in length wasused as a transparent substrate. A diluted solution for an alignmentlayer (a polymer of the structural formula below) was continuouslyapplied to one side of the transparent substrate to form an orthogonalalignment layer having a thickness of 0.5 μm. Then, a rubbing processwas continuously performed in a direction at 16° clockwise with respectto the longitudinal direction of the transparent substrate.

[0394] Polymer PA-132 for the Orthogonal Alignment Layer

[0395] (Preparation of an Optically Anisotropic Layer (A))

[0396] A coating solution of the composition below was continuouslyapplied to the alignment layer using a bar coater, and dried and heated(matured in alignment), and further irradiated with UV rays to form anoptically anisotropic layer (A) having a thickness of 1.6 μm. Theoptically anisotropic layer had a slow axis in a direction at 74°anticlockwise with respect to the longitudinal direction of thetransparent substrate.

[0397] The retardation value at 550 nm was 225 nm.

[0398] Composition of the Coating Solution for the Optically AnisotropicLayer Rod-like liquid crystal compound (1) below 14.5 wt % Sensitizer(1) below 1.0 wt % Photo-polymerization initiator (1) below 3.0 wt % Anagent for promoting homogenous alignment (1) bellow 1.0 wt % Methylethyl ketone 80.5 wt %

[0399] Rod-Like Liquid Crystal Compound (1)

[0400] Sensitizer (1)

[0401] Photo-Polymerization Initiator (1)

[0402] Agent for Promoting Homogenous Alignment (1)

Example 2

[0403] (Forming an Alignment Layer)

[0404] An optically isotropic triacetyl cellulose film in the form of aroll of 100 μm in thickness, 500 mm in width and 500 m in length wasused as a transparent substrate. A diluted solution for an alignmentlayer (a polymer of the structural formula below) was continuouslyapplied to one side of the transparent substrate to form an orthogonalalignment layer having a thickness of 0.8 μm. Then, a rubbing processwas continuously performed in a direction at 16° clockwise with respectto the longitudinal direction of the transparent substrate.

[0405] Polymer PA-132 for the Orthogonal Alignment Layer

[0406] A coating solution of the composition below was continuouslyapplied to the alignment layer using a bar coater, and dried and heated(matured in alignment), and further irradiated with UV rays to form anoptically anisotropic layer (A) having a thickness of 1.6 μm. Theoptically anisotropic layer had a slow axis in a direction at 74°anticlockwise with respect to the longitudinal direction of thetransparent substrate. The retardation value at 550 nm was 224 nm.

[0407] Composition of the Coating Solution for the Optically AnisotropicLayer Rod-like liquid crystal compound (1) above 14.5 wt % Sensitizer(1) above 1.0 wt % Photo-polymerization initiator (1) above 3.0 wt %Agent for promoting homogenous alignment (1) above 1.0 wt % Methyl ethylketone 80.5 wt %

Example 3

[0408] (Forming an Alignment Layer)

[0409] An optically isotropic triacetyl cellulose film in the form of aroll of 100 μm in thickness, 500 mm in width and 30 m in length was usedas a transparent substrate. A diluted solution for an alignment layer (apolymer of the structural formula below) was continuously applied to oneside of the transparent substrate to form an alignment layer having athickness of 0.5 μm. Then, a rubbing treatment was continuouslyperformed in a direction at 16° clockwise with respect to thelongitudinal direction of the transparent substrate.

[0410] Polymer for the Alignment Layer

[0411] (Preparation of an Optically Anisotropic Layer (B))

[0412] A coating solution of the composition below was continuouslyapplied to the alignment layer using a bar coater, and dried and heated(matured in alignment), and further irradiated with UV rays to form anoptically anisotropic layer (B) having a thickness of 0.8 μm. Theoptically anisotropic layer had a slow axis parallel to the rubbingdirection, i.e. in a direction at 16° with respect to the longitudinaldirection of the transparent substrate. The retardation value at 550 nmwas 113 nm.

[0413] Composition of the Coating Solution for the Optically AnisotropicLayer Rod-like liquid crystal compound (1) above 13.0 wt % Sensitizer(1) above 1.0 wt % Photo-polymerization initiator (1) above 3.0 wt %Agent for promoting homogenous alignment (1) above 1.0 wt % Methyl ethylketone 82.0 wt %

Example 4

[0414] The diluted solution for an alignment layer used in Example 3 wascontinuously applied on the optically anisotropic layer of the retarderprepared in Example 1 to form an alignment layer. Then, the alignmentlayer was subjected to a rubbing treatment at 58° clockwise with respectto the slow axis of the optically anisotropic layer (A) and 16°anticlockwise with respect to the longitudinal direction of the retarderprepared in Example 1.

[0415] Then, the coating solution of a liquid crystal compound used inExample 3 was continuously applied on the alignment layer using a barcoater, and dried and heated (matured in alignment), and furtherirradiated with UV rays to form an optically anisotropic layer (B)having a thickness of 0.8 μm.

Example 5

[0416] The diluted solution for an alignment layer used in Example 3 wascontinuously applied on the optically anisotropic layer of the retarderprepared in Example 2 to form an alignment layer. Then, the alignmentlayer was subjected to a rubbing treatment at 58° clockwise with respectto the slow axis of the optically anisotropic layer (A) and 16°anticlockwise with respect to the longitudinal direction of the retarderprepared in Example 2.

[0417] Then, the coating solution of a liquid crystal compound used inExample 3 was continuously applied to the alignment layer using a barcoater, and dried and heated (matured in alignment), and furtherirradiated with UV rays to form an optically anisotropic layer (B)having a thickness of 0.8 μm.

Comparative Example 1

[0418] The same diluted solution as used in Example 3 was used to forman alignment layer. Then, a rubbing treatment was continuously performedin a direction at 74° anticlockwise with respect to the longitudinaldirection of the transparent substrate.

[0419] A coating solution of the same composition as used in Example 3was continuously applied on the alignment layer using a bar coater, anddried and heated (matured in alignment), and further irradiated with UVrays to form an optically anisotropic layer (A) having a thickness of1.6 μm. The optically anisotropic layer had a slow axis in a directionat 74° with respect to the longitudinal direction of the transparentsubstrate. The retardation value at 550 nm was-225 nm.

[0420] The diluted solution for an alignment layer used in Example 3 wascontinuously applied to the optically anisotropic layer (A) of theretarder to form an alignment layer. Then, the alignment layer wassubjected to a rubbing treatment at 58° clockwise with respect to theslow axis of the optically anisotropic layer (A) and 16° anticlockwisewith respect to the longitudinal direction of the retarder.

[0421] Then, the coating solution of a liquid crystal compound used inExample 3 was continuously applied to the alignment layer using a barcoater, and dried and heated (matured in alignment), and furtherirradiated with UV rays to form an optically anisotropic layer (B)having a thickness of 0.8 μm. The retardation value of the opticallyanisotropic layer (B) was 113 nm, and the angle between the twoanisotropic layers was 58°.

Comparative Example 2

[0422] A retarder was formed exactly in the same manner as in Example 4except that the agent for promoting homogenous alignment was excludedfrom the optically anisotropic layers (A) and (B). The angle between thetwo anisotropic layers was adjusted to 58°, but the retardation value ofthe optically anisotropic layer (A) was 180 nm and the retardation valueof the optically anisotropic layer (B) was 73 nm, showing that theretarder did not have a sufficient optical performance for λ/4 plates.

Example 6 Evaluation of the Retarders

[0423] The retarders prepared in Examples 4, 5 and Comparative examples1, 2 were each laminated to a polarizer consisting of a polarizing filmand a protective film at an angle of 90° between the polarization axisof the polarizing film and the longitudinal direction of the retarder,i.e. in a roll-to-roll manner to prepare circular polarizers. Theresulting circular polarizers were irradiated (at wavelengths of 450 nm,550 nm and 650 nm) from the side of the polarizing film to determine thephase shift (retardation value: Re) of the transmitted light. Theresults are shown in the table below. TABLE 1 Re (450 nm) Re (550 nm) Re(630 nm) Desired 112.5 nm 137.5 nm 157.5 nm Value Example 4 112 nm 135nm 143 nm Example 5 110 nm 135 nm 14 mm Comparative 98 nm 119 nm 126 nmExample 1 Comparative 105 nm 130 nm 132 nm Example 2

[0424] As shown in the table above, the retarders prepared in Examples 4and 5 show a phase shift of π/2 especially in the short wavelengthregion. The retarders prepared in Comparative examples 1 and 2 were poorin the alignment condition of the liquid crystals and showed manyalignment defects. It is shown that the phase shift also decreased inthe whole wavelength region.

[0425] Having described our invention as related to the presentembodiments, it is our intention that the invention not be limited byany of the details of the description, unless otherwise specified, butrather be construed broadly within its spirit and scope as set out inthe accompanying claims.

What is claimed is:
 1. A retarder comprising: a long transparentsubstrate; and up on the substrate, a first optically anisotropic layerformed from a homogenously aligned rod-like liquid crystal compound andhaving a phase shift substantially equal ton measured at a wavelength of550 nm; a second optically anisotropic layer formed form a homogenouslyaligned rod-like liquid crystal compound and having a phase shiftsubstantially equal to π/2 measured at a wavelength of 550 nm; and afirst alignment layer having a rubbing axis defining the azimuthaldirection of the homogenous alignment of the rod-like liquid crystalcompound in the first optically anisotropic layer; wherein the anglebetween the slow axis in the plane of the first optically anisotropiclayer and the longitudinal direction of the transparent substrate issubstantially 75°, the angle between the slow axis in the plane of thesecond optically anisotropic layer and the longitudinal direction of thetransparent substrate is substantially 15°, the angle between the slowaxis in the plane of the second optically anisotropic layer and the slowaxis in the plane of the first optically anisotropic layer issubstantially 60° and the azimuthal direction of the homogenousalignment of the rod-like liquid crystal compound in the first opticallyanisotropic layer is substantially orthogonal to the rubbing axis of thefirst alignment layer.
 2. The retarder of claim 1, comprising a secondalignment layer having a rubbing axis defining the azimuthal directionof the homogenous alignment of the rod-like liquid crystal compound inthe second optically anisotropic layer, wherein the angle between therubbing axis of the first alignment layer and the longitudinal directionof the transparent substrate is substantially −15° and the angle betweenthe rubbing axis of the second alignment layer and the longitudinaldirection of the transparent substrate is substantially 15°.
 3. Theretarder of claim 1 wherein the first alignment layer is formed of atleast one copolymer having at least one of repeating units representedby any one of formulae (I) to (III) below and at least one of repeatingunits represented by formula (IV) below:

wherein R¹ to R³ independently represent a hydrogen atom, a halogen atomor an alkyl group having 1 to 6 carbon atoms; M represents a proton, analkali metal ion or an ammonium ion; L⁰ and L¹ independently represent adivalent linking group selected from the group consisting of —O—, —S—,—CO—, —NR⁴—, —SO₂—, alkylene groups, alkenylene groups, arylene groupsand combinations thereof; R⁴ represents a hydrogen atom or an alkylgroup containing 1 to 6 carbon atoms; R⁰ represents a C10-100 groupcontaining at least two aromatic rings or aromatic heterocycles; Cyrepresents a condensed aromatic cyclic hydrocarbon group or a condensedaromatic heterocyclic group; Q represents a polymerizable group; and m,n¹, n² and p represent the mol % of each repeating unit where m is 10-99mol %, n¹ and n² are each 1-90 mol % and p is 0.1-20 mol %.
 4. Theretarder of claim 1 wherein the first optically anisotropic layercontains at least an agent for promoting homogenous alignmentrepresented by formula (V) below: (Hb-L²-)_(n)B¹  Formula (V) wherein Hbrepresents an aliphatic group having 6 to 40 carbon atoms or analiphatic-substituted oligosiloxanoxy group having 6 to 40 carbon atoms;L² represents a divalent linking group selected from the groupconsisting of —O—, —S—, —CO—, —NR⁵—, —SO₂—, alkylene groups, alkenylenegroups, arylene groups and combinations thereof; R⁵ represents ahydrogen atom or an alkyl group having 1 to 6 carbon atoms; n representsan integer of any of 2 to 12; and B¹ represents an n-valent groupcontaining at least three cyclic structures; and wherein the tilt angleof the rod-like liquid crystal compound is substantially less than 10°.5. The retarder of claim 1 wherein the rod-like liquid crystal compoundin the first optically anisotropic layer or the second opticallyanisotropic layer is at least one of rod-like liquid crystal compoundsof formula (VI) below:Q¹¹-L¹¹-Cy¹¹-L¹²-(Cy¹²-L¹³)_(n)-Cy¹³-L¹⁴-Q¹²  Formula (VI) wherein Q¹¹and Q¹² independently represent a polymerizable group; L¹¹ and L¹⁴independently represent a divalent linking group; L¹² and L¹³independently represent a single bond or a divalent linking group; Cy¹¹,Cy¹² and Cy¹³ independently represent a divalent cyclic group; and nrepresents 0, 1 or
 2. 6. A method for preparing a retarder comprisingthe steps of: forming a first alignment layer up on a long transparentsubstrate, said first alignment layer having a rubbing axis at an angleof substantially −15° with respect to the longitudinal direction of thetransparent substrate, forming a first optically anisotropic layer byapplying a rod-like liquid crystal compound to the first alignment layerand homogenously aligning the rod-like liquid crystal compound in anazimuthal direction substantially orthogonal to the rubbing axis of thefirst alignment layer, so as that the first optically anisotropic layerhas a phase shift substantially equal to π measured at a wavelength of550 nm, forming a second alignment layer on the transparent substrate,said second alignment layer having a rubbing axis at an angle ofsubstantially 15° with respect to the longitudinal direction of thetransparent substrate, and forming a second optically anisotropic layerby applying a rod-like liquid crystal compound to the second alignmentlayer and homogenously aligning the rod-like liquid crystal compound inan azimuthal direction substantially parallel to the rubbing axis of thesecond alignment layer, so as that the second optically anisotropiclayer has a phase shift substantially equal to π/2 measured at awavelength of 550 nm.
 7. The method of claim 6 wherein the step offorming a first alignment layer and the step of forming a firstoptically anisotropic layer are followed by the step of forming a secondalignment layer and the step of forming a second optically anisotropiclayer.
 8. The method of claim 6 wherein the step of forming a secondalignment layer and the step of forming a second optically anisotropiclayer are followed by the step of forming a first alignment layer andthe step of forming a first optically anisotropic layer.
 9. The methodof claim 6 wherein both steps of forming a first optically anisotropiclayer and a second optically anisotropic layer are steps of forming themby applying a composition comprising the rod-like liquid crystalcompound and at least an agent for promoting homogenous alignmentrepresented by formula (V) below: (Hb-L²-)_(n)B¹  Formula (V) wherein Hbrepresents an aliphatic group having 6 to 40 carbon atoms or analiphatic-substituted oligosiloxanoxy group having 6 to 40 carbon atoms;L² represents a divalent linking group selected from the groupconsisting of —O—, —S—, —CO—, —NR⁵—, —SO₂—, alkylene groups, alkenylenegroups, arylene groups and combinations thereof; R⁵ represents ahydrogen atom or an alkyl group having 1 to 6 carbon atoms; n representsan integer of any of 2 to 12; and B¹ represents an n-valent groupcontaining at least three cyclic structures; and homogenously aligningthe rod-like liquid crystal compound in the presence of the agent, so asthat the tilt angle of the rod-like liquid crystal compound issubstantially less than 10°.
 10. The method of claim 6 wherein the firstalignment layer is formed of at least one copolymer having at least oneof repeating units represented by any one of formulae (I) to (III) belowand at least one of repeating units represented by formula (IV) below:

wherein R¹ to R³ independently represent a hydrogen atom, a halogen atomor an alkyl group having 1 to 6 carbon atoms; M represents a proton, analkali metal ion or an ammonium ion; L⁰ and L¹ independently represent adivalent linking group selected from the group consisting of —O—, —S—,—CO—, —NR⁴—, —SO₂—, alkylene groups, alkenylene groups, arylene groupsand combinations thereof; R⁴ represents a hydrogen atom or an alkylgroup containing 1 to 6 carbon atoms; R⁰ represents a C10-100 groupcontaining at least two aromatic rings or aromatic heterocycles; Cyrepresents a condensed aromatic cyclic hydrocarbon group or a condensedaromatic heterocyclic group; Q represents a polymerizable group; and m,n¹, n² and p represent the mol % of each repeating unit where m is 10-99mol %, n¹ and n² are each 1-90 mol % and p is 0.1-20 mol %.
 11. Acircular polarizer comprising: a long transparent substrate having afront surface and rear surface; and up on the front surface of thesubstrate, a first optically anisotropic layer formed of a homogenouslyaligned rod-like liquid crystal compound and having a phase shiftsubstantially equal to π measured at a wavelength of 550 nm; a secondoptically anisotropic layer formed of a homogenously aligned rod-likeliquid crystal compound and having a phase shift substantially equal toπ/2 measured at a wavelength of 550 nm; and a first alignment layerhaving a rubbing axis defining the azimuthal direction of the homogenousalignment of the rod-like liquid crystal compound in the first opticallyanisotropic layer; and on the rear surface of the substrate, apolarizing film having a polarization axis substantially orthogonal tothe longitudinal direction of the substrate; wherein the angle betweenthe slow axis in the plane of the first optically anisotropic layer andthe longitudinal direction of the transparent substrate is substantially75°, the angle between the slow axis in the plane of the secondoptically anisotropic layer and the longitudinal direction of thetransparent substrate is substantially 15°, the angle between the slowaxis in the plane of the second optically anisotropic layer and the slowaxis in the plane of the first optically anisotropic layer issubstantially 60° and the azimuthal direction of the homogenousalignment of the rod-like liquid crystal compound in the first opticallyanisotropic layer is substantially orthogonal to the rubbing axis of thefirst alignment layer.
 12. The circular polarizer of claim 11,comprising a second alignment layer having a rubbing axis defining theazimuthal direction of the homogenous alignment of the rod-like liquidcrystal compound in the second optically anisotropic layer, wherein theangle between the rubbing axis of the first alignment layer and thelongitudinal direction of the transparent substrate is substantially−15° and the angle between the rubbing axis of the second alignmentlayer and the longitudinal direction of the transparent substrate issubstantially 15°.
 13. The circular polarizer of claim 11 wherein thefirst alignment layer contains at least one copolymer having at leastone of repeating units represented by any one of formulae (I) to (III)below and at least one of repeating units represented by formula (IV)below:

wherein R¹ to R³ independently represent a hydrogen atom, a halogen atomor an alkyl group having 1 to 6 carbon atoms; M represents a proton, analkali metal ion or an ammonium ion; L⁰ and L¹ independently represent adivalent linking group selected from the group consisting of —O—, —S—,—CO—, —NR⁴—, —SO₂—, alkylene groups, alkenylene groups, arylene groupsand combinations thereof; R⁴ represents a hydrogen atom or an alkylgroup containing 1 to 6 carbon atoms; R⁰ represents a C10-100 groupcontaining at least two aromatic rings or aromatic heterocycles; Cyrepresents a condensed aromatic cyclic hydrocarbon group or a condensedaromatic heterocyclic group; Q represents a polymerizable group; and m,n¹, n² and p represent the mol % of each repeating unit where m is 10-99mol %, n¹ and n² are each 1-90 mol % and p is 0.1-20 mol %.
 14. Thecircular polarizer of claim 11 wherein the first optically anisotropiclayer contains at least an agent for promoting homogenous alignmentrepresented by formula (V) below: (Hb-L²-)_(n)B¹  Formula (V) wherein Hbrepresents an aliphatic group having 6 to 40 carbon atoms or analiphatic-substituted oligosiloxanoxy group having 6 to 40 carbon atoms;L² represents a divalent linking group selected from the groupconsisting of —O—, —S—, —CO—, —NR⁵—, —SO₂—, alkylene groups, alkenylenegroups, arylene groups and combinations thereof; R⁵ represents ahydrogen atom or an alkyl group having 1 to 6 carbon atoms; n representsan integer of any of 2 to 12; and B¹ represents an n-valent groupcontaining at least three cyclic structures; and wherein the tilt angleof the rod-like liquid crystal compound is substantially less than 10°.15. The circular polarizer of claim 11 wherein the rod-like liquidcrystal compound in the first optically anisotropic layer or the secondoptically anisotropic layer is at least one of rod-like liquid crystalcompounds of formula (VI) below:Q¹¹-L¹¹-Cy¹¹-L¹²-(Cy¹²-L¹³)_(n)-Cy¹³-L¹⁴-Q¹²  Formula (VI) wherein Q¹¹and Q¹² independently represent a polymerizable group; L¹¹ and L¹⁴independently represent a divalent linking group; L¹² and L¹³independently represent a single bond or a divalent linking group; Cy¹¹,Cy¹² and Cy¹³ independently represent a divalent cyclic group; and nrepresents 0, 1 or
 2. 16. A method for preparing a circular polarizercomprising the steps of: forming a first alignment layer up on a frontsurface of a long transparent substrate, said first alignment layerhaving a rubbing axis at an angle of substantially −15° with respect tothe longitudinal direction of the transparent substrate, forming a firstoptically anisotropic layer by applying a rod-like liquid crystalcompound to the first alignment layer and homogenously aligning therod-like liquid crystal compound in an azimuthal direction substantiallyorthogonal to the rubbing axis of the first alignment layer, so as thatthe first optically anisotropic layer has a phase shift substantiallyequal to π measured at a wavelength of 550 nm, forming a secondalignment layer on the transparent substrate, said second alignmentlayer having a rubbing axis at an angle of substantially 15° withrespect to the longitudinal direction of the transparent substrate,forming a second optically anisotropic layer by applying a rod-likeliquid crystal compound to the second alignment layer and homogenouslyaligning the rod-like liquid crystal compound in an azimuthal directionsubstantially parallel to the rubbing axis of the second alignmentlayer, so as that the second optically anisotropic layer has a phaseshift substantially equal to π/2 measured at a wavelength of 550 nm, andforming a polarizing film on a rear surface of the substrate, having anabsorption axis substantially parallel to the longitudinal direction ofthe transparent substrate and a polarization axis in a directionsubstantially perpendicular to the longitudinal direction of thetransparent substrate.
 17. The method of claim 16 wherein the step offorming a first alignment layer and the step of forming a firstoptically anisotropic layer are followed by the step of forming a secondalignment layer and the step of forming a second optically anisotropiclayer.
 18. The method of claim 16 wherein the step of forming a secondalignment layer and the step of forming a second optically anisotropiclayer are followed by the step of forming a first alignment layer andthe step of forming a first optically anisotropic layer.
 19. The methodof claim 16 wherein both steps of forming a first optically anisotropiclayer and a second optically anisotropic layer are forming them byapplying a composition comprising the rod-like liquid crystal compoundand at least an agent for promoting homogenous alignment represented byformula (V) below: (Hb-L²-)_(n)B¹  Formula (V) wherein Hb represents analiphatic group having 6 to 40 carbon atoms or an aliphatic-substitutedoligosiloxanoxy group having 6 to 40 carbon atoms; L² represents adivalent linking group selected from the group consisting of —O—, —S—,—CO—, —NR⁵—, —SO₂—, alkylene groups, alkenylene groups, arylene groupsand combinations thereof; R⁵ represents a hydrogen atom or an alkylgroup having 1 to 6 carbon atoms; n represents an integer of any of 2 to12; and B¹ represents an n-valent group containing at least three cyclicstructures; and homogenously aligning the rod-like liquid crystalcompound in the presence of the agent, so as that the tilt angle of therod-like liquid crystal compound is substantially less than 10°.
 20. Themethod of claim 16 wherein the first alignment layer is formed of atleast one copolymer having at least one of repeating units representedby any one of formulae (I) to (III) below and at least one of repeatingunits represented by formula (IV) below:

wherein R¹ to R³ independently represent a hydrogen atom, a halogen atomor an alkyl group having 1 to 6 carbon atoms; M represents a proton, analkali metal ion or an ammonium ion; L⁰ and L¹ independently represent adivalent linking group selected from the group consisting of —O—, —S—,—CO—, —NR⁴—, —SO₂—, alkylene groups, alkenylene groups, arylene groupsand combinations thereof; R⁴ represents a hydrogen atom or an alkylgroup containing 1 to 6 carbon atoms; R⁰ represents a C10-100 groupcontaining at least two aromatic rings or aromatic heterocycles; Cyrepresents a condensed aromatic cyclic hydrocarbon group or a condensedaromatic heterocyclic group; Q represents a polymerizable group; and m,n¹, n² and p represent the mol % of each repeating unit where m is 10-99mol %, n¹ and n² are each 1-90 mol % and p is 0.1-20 mol %.
 21. A devisecomprising: a long transparent substrate having a front surface and rearsurface; and up on the front surface of the substrate, a first opticallyanisotropic layer formed of a homogenously aligned rod-like liquidcrystal compound and having a phase shift substantially equal to πmeasured at a wavelength of 550 nm; a second optically anisotropic layerformed of a homogenously aligned rod-like liquid crystal compound andhaving a phase shift substantially equal to π/2 measured at a wavelengthof 550 nm; and a first alignment layer having a rubbing axis definingthe azimuthal direction of the homogenous alignment of the rod-likeliquid crystal compound in the first optically anisotropic layer; and onthe rear surface of the substrate, a polarizing film having apolarization axis substantially orthogonal to the longitudinal directionof the substrate; wherein the angle between the slow axis in the planeof the first optically anisotropic layer and the longitudinal directionof the transparent substrate is substantially 75°, the angle between theslow axis in the plane of the second optically anisotropic layer and thelongitudinal direction of the transparent substrate is substantially15°, the angle between the slow axis in the plane of the secondoptically anisotropic layer and the slow axis in the plane of the firstoptically anisotropic layer is substantially 60° and the azimuthaldirection of the homogenous alignment of the rod-like liquid crystalcompound in the first optically anisotropic layer is substantiallyorthogonal to the rubbing axis of the first alignment layer.